Articoli di riviste: "DFT and TB"

1

Duarte, Hélio A., Thomas Heine e Gotthard Seifert. "DFT ×TB − a unified quantum-mechanical hybrid method". Theoretical Chemistry Accounts 114, n. 1-3 (12 maggio 2005): 68–75. http://dx.doi.org/10.1007/s00214-005-0645-0.

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Bhatt, Nisarg K., A. B. Patel, A. Y. Vahora, P. R. Vyas, B. Y. Thakore e Ashvin R. Jani. "Structural and Vibrational Properties of FeO Using First-Principles". Advanced Materials Research 665 (febbraio 2013): 49–52. http://dx.doi.org/10.4028/www.scientific.net/amr.665.49.

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We have studied the equation of states and vibrational properties of FeO using DFT based plane-wave pseudopotential (PW-DFT) within the generalized gradient approximation. The calculated cohesive properties at ambient condition, namely, lattice constant (a0), bulk modulus (B0) and its first pressure derivative (), are reported for B1-phase of FeO, in agreement with previous experimental and other theoretical results. A linear-response approach to the density functional theory was used to derive the phonon frequencies and phonon density of state (p-dos). Further, in order to calculate both static and dynamic equations of states, nearest-neighbour second-moment tight-binding energy model (TB-SMA) was used. Parameters of the present TB-SMA model were determined by the presentab initiopseudopotential calculations. It is found that the present simple TB-SMA scheme is able to mimic shock Hugoniot for such oxides correctly.

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Asadi-Aghbolaghi, Narges, Johann Pototschnig, Zahra Jamshidi e Lucas Visscher. "Effects of ligands on (de-)enhancement of plasmonic excitations of silver, gold and bimetallic nanoclusters: TD-DFT+TB calculations". Physical Chemistry Chemical Physics 23, n. 33 (2021): 17929–38. http://dx.doi.org/10.1039/d1cp03220h.

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Chen, Peng, Jin-Yu Zou e Bang-Gui Liu. "Intrinsic ferromagnetism and quantum anomalous Hall effect in a CoBr2monolayer". Physical Chemistry Chemical Physics 19, n. 21 (2017): 13432–37. http://dx.doi.org/10.1039/c7cp02158e.

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The electronic, magnetic, and topological properties of a CoBr₂monolayer are studied in the framework of density-functional theory (DFT) combined with tight-binding (TB) modeling in terms of the Wannier basis.

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Shah, Saima Ahmad, Mudasser Husain, Nasir Rahman, Mohammad Sohail, Rajwali Khan, Abid Ali Khan, Asad Ullah et al. "Insight into the exemplary structural, elastic, electronic and optical nature of GaBeCl₃ and InBeCl₃: a DFT study". RSC Advances 12, n. 13 (2022): 8172–77. http://dx.doi.org/10.1039/d2ra00943a.

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In the scheme of density functional theory (DFT), Structural, elastic, electronic, and optical properties calculations of GaBeCl3 and InBeCl3 are carried out using Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) installed in Wein2k software.

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Mendoza-Huizar, Luis. "A DFT study of the chemical reactivity of thiobencarb and its oxidized derivatives in aqueous phase". Journal of the Serbian Chemical Society 83, n. 9 (2018): 981–93. http://dx.doi.org/10.2298/jsc170927034m.

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In the present work, the global and local reactivity of S-(4-chlorobenzyl)- N,N-diethylthiocarbamate (TB) and its oxidized derivatives (sulfone (TBSu) and sulfoxide (TBS) were analyzed. In addition, the chemical reactivities of the dechlorinated forms of TB (DTB), TBSu (DTBSu) and TBS (DTBS) were studied. The calculations were performed at the wB97XD/6- -311++G(2d,2p) level of theory in the aqueous phase. The condensed Fukui functions indicated that for TB and DTB, the most preferred sites for donating electron in a reaction are located on the S and N atoms, while the most reactive sites for accepting electrons are associated with the aromatic ring (AR). For TBS and DTBS, the more reactive sites are located on AR, S and AR for nucleophilic, electrophilic and free radical attacks, respectively. In the case of TBSu and DTBSu, the results showed AR to be the more reactive zone for the three kinds of attacks. These last results suggest that cleavage of the C?S bond in TB, TBS and their dechlorinated forms is favored by electrophilic attacks. Additionally, the obtained results suggest that in TB, it is plausible that the cleavage of the C?N is favored on attack of this molecule by electrophiles.

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Rai, D. P., A. Shankar, Sandeep Sandeep, M. P. Ghimire, R. Khenata e R. K. Thapa. "Study of the enhanced electronic and thermoelectric (TE) properties of ZrxHf1−x−yTayNiSn: a first principles study". RSC Advances 5, n. 115 (2015): 95353–59. http://dx.doi.org/10.1039/c5ra12897h.

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A density functional theory (DFT) approach employing generalized gradient approximation (GGA) and the modified Becke Johnson (TB-mBJ) potential has been used to study the electronic and thermoelectric (TE) properties of Zr_xHf_1−x−yTa_yNiSn.

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Rahnamaye Aliabad, H. A., Z. Barzanuni, S. Ramezani Sani, Iftikhar Ahmad, S. Jalali-Asadabadi, H. Vaezi e M. Dastras. "Thermoelectric and phononic properties of (Gd, Tb) MnO3 compounds: DFT calculations". Journal of Alloys and Compounds 690 (gennaio 2017): 942–52. http://dx.doi.org/10.1016/j.jallcom.2016.08.167.

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Gao, Fei, Eric J. Bylaska e William J. Weber. "Defect Properties in GaN: Ab Initio and Empirical Potential Calculations". Materials Science Forum 475-479 (gennaio 2005): 3087–90. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3087.

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The defect properties and atomic configurations in GaN have been comparatively investigated using density functional theory (DFT) and molecular dynamics method with two representative potentials. The DFT calculations show that the relaxation of vacancies is generally small, but the relaxation around antisite defects is large. The N interstitials, starting from any possible configurations, eventually relax into a N+-N< 0 2 11 > split interstitial. In the case of Ga interstitials, the most stable configuration is a Ga octahedral interstitial, but the Ga+-Ga< 0 2 11 > split interstitial can bridge the gap between non-bounded Ga atoms. The formation energies of vacancies and antisite defects obtained using the Stillinger-Weber potential (SW) are in reasonable agreement with those obtained by DFT calculations, whereas the Tersoff-Brenner (TB) potential better describes the behavior of N interstitials.

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Asadi-Aghbolaghi, Narges, Robert Rüger, Zahra Jamshidi e Lucas Visscher. "TD-DFT+TB: An Efficient and Fast Approach for Quantum Plasmonic Excitations". Journal of Physical Chemistry C 124, n. 14 (24 marzo 2020): 7946–55. http://dx.doi.org/10.1021/acs.jpcc.0c00979.

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Lee, Hunpyo, Jahyun Koo, Massimo Capone, Yongkyung Kwon e Hoonkyung Lee. "DFT and TB study of the geometry of hydrogen adsorbed on graphynes". Journal of Physics: Condensed Matter 26, n. 38 (4 settembre 2014): 385301. http://dx.doi.org/10.1088/0953-8984/26/38/385301.

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Ziella, D. H., M. C. Caputo e P. F. Provasi. "Study of geometries and electronic properties of AgSin clusters using DFT/TB". International Journal of Quantum Chemistry 111, n. 7-8 (8 settembre 2010): 1680–93. http://dx.doi.org/10.1002/qua.22815.

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Lukoyanov, Alexey V., Lubov N. Gramateeva, Yury V. Knyazev, Yury I. Kuz’min, Sachin Gupta e K. G. Suresh. "Effect of Electronic Correlations on the Electronic Structure, Magnetic and Optical Properties of the Ternary RCuGe Compounds with R = Tb, Dy, Ho, Er". Materials 13, n. 16 (11 agosto 2020): 3536. http://dx.doi.org/10.3390/ma13163536.

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In this study, the ab initio and experimental results for RCuGe ternary intermetallics were reported for R = Tb, Dy, Ho, Er. Our theoretical calculations of the electronic structure, employing local spin density approximation accounting for electron–electron correlations in the 4f shell of Tb, Dy, Ho, Er ions were carried in DFT+U method. The optical properties of the RCuGe ternary compounds were studied at a broad range of wavelengths. The spectral and electronic characteristics were obtained. The theoretical electron densities of states were taken to interpret the experimental energy dependencies of the experimental optical conductivity in the interband light–absorption region. From the band calculations, the 4f shell of the rare-earth ions was shown to provide the major contribution to the electronic structure, magnetic and optical properties of the RCuGe intermetallics. The accounting for electron–electron correlations in Tb, Dy, Ho, Er resulted in a good agreement between the calculated and experimental magnetic and optical characteristics.

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Zheng, He-Qi, Lin Zhang, Mengting Lu, Xiaoyan Xiao, Yu Yang, Yuanjing Cui e Guodong Qian. "Precise Design and Deliberate Tuning of Turn-On Fluorescence in Tetraphenylpyrazine-Based Metal−Organic Frameworks". Research 2022 (17 ottobre 2022): 1–11. http://dx.doi.org/10.34133/2022/9869510.

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The manipulation on turn-on fluorescence in solid state materials attracts increasing interests owing to their widespread applications. Herein we report how the nonradiative pathways of tetraphenylpyrazine (TPP) units in metal−organic frameworks (MOFs) systems could be hindered through a topological design approach. Two MOFs single crystals of different topology were constructed via the solvothermal reaction of a TPP-based 4,4′,4″,4‴-(pyrazine-2,3,5,6-tetrayl) tetrabenzoic acid (H4TCPP) ligand and metal cations, and their mechanisms of formation have been explored. Compared with the innate low-frequency vibrational modes of flu net Tb-TCPP-1, such as phenyl ring torsions and pyrazine twists, Tb-TCPP-2 adopts a shp net, so the dihedral angle of pyrazine ring and phenyl arms is larger, and the center pyrazine ring in TPP unit is coplanar, which hinders the radiationless decay of TPP moieties in Tb-TCPP-2. Thereby Tb-TCPP-2 exhibits a larger blue-shifted fluorescence and a higher fluorescence quantum yield than Tb-TCPP-1, which is consistent with the reduced nonradiative pathways. Furthermore, Density functional theory (DFT) studies also confirmed aforementioned tunable turn-on fluorescence mechanism. Our work constructed TPP-type MOFs based on a deliberately topological design approach, and the precise design of turn-on fluorescence holds promise as a strategy for controlling nonradiative pathways.

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CHIGO-ANOTA, E., A. FLORES-RIVEROS e J. F. RIVAS-SILVA. "LSDA+U APPROXIMATION-BASED ANALYSIS OF THE ELECTRONIC STRUCTURE OF CeFeGe3". International Journal of Modern Physics B 20, n. 03 (30 gennaio 2006): 287–301. http://dx.doi.org/10.1142/s0217979206033243.

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We perform ab initio electronic structure calculations of the intermetallic compound CeFeGe 3 by means of the Tight Binding Linear Muffin-Tin Orbitals-Atomic Sphere Approximation (TB-LMTO-ASA) within the Local Spin Density Approximation containing the so-called Hubbard correction term ( LSDA+U SIC), using the Stuttgart's TB (Tight Binding)-LMTO-ASA code in the framework of the Density Functional Theory (DFT). At the LSDA-vBH level, our electronic structure calculations indicate an intermediate valence character compound whereas a DOS (density of states) analysis favors its metallic nature. We also study electronic correlation effects via the introduction of the U parameter on Ce and Fe , where a metallic and magnetic characters for this compound are found, along with certain features that may possibly be associated with a heavy fermion system.

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Arshad Javid, M., Zafar Ullah Khan, Zahid Mehmood, Azeem Nabi, Fayyaz Hussain, M. Imran, Muhammad Nadeem e Naeem Anjum. "Structural, electronic and optical properties of LiNbO3 using GGA-PBE and TB-mBJ functionals: A DFT study". International Journal of Modern Physics B 32, n. 14 (5 giugno 2018): 1850168. http://dx.doi.org/10.1142/s0217979218501680.

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In the present work, first-principles calculations were performed to obtain the structural, electronic and optical properties of lithium niobate crystal using two exchange-correlation functionals (GGA-PBE and TB-mBJ). The calculated structural parameters were very close to the experimental values. TB-mBJ functional was found to be good when compared to LDA and GGA functionals in case of bandgap energy of 3.715 eV of lithium niobate. It was observed that the upper valence and lower conduction bands consist mainly the O-2p and Nb-4[Formula: see text] states, respectively. Furthermore, calculations for real and imaginary parts of frequency-dependent dielectric function [Formula: see text] of lithium niobate crystal were performed using TD-DFT method. The ordinary refractive index n[Formula: see text], extraordinary refractive index n[Formula: see text], its birefringence and absorption peaks in imaginary dielectric function [Formula: see text] were also calculated.

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Rehman, Gul, M. Shafiq, Saifullah, Rashid Ahmad, S. Jalali-Asadabadi, M. Maqbool, Imad Khan, H. Rahnamaye-Aliabad e Iftikhar Ahmad. "Electronic Band Structures of the Highly Desirable III–V Semiconductors: TB-mBJ DFT Studies". Journal of Electronic Materials 45, n. 7 (5 maggio 2016): 3314–23. http://dx.doi.org/10.1007/s11664-016-4492-7.

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Mehta, Shreya, e Sapan Mohan Saini. "Electronic, structural and optical properties of rare-earth based TbNiSb half Heusler compound". Journal of Physics: Conference Series 2576, n. 1 (1 settembre 2023): 012007. http://dx.doi.org/10.1088/1742-6596/2576/1/012007.

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Abstract Half-Heusler (HH) compounds have potential applications in many fields including spintronics and future energy applications. Rare earth based Heusler materials are best suitable for thermoelectric materials. To calculate some physical properties (the electronic, optical-properties) of rare earth (RE) based ternary HH TbNiSb compound, we applied full potential linearized augmented plane wave (FPLAPW) method which is based on Density Functional Theory (DFT). We use the Coulomb corrected generalized gradient approximation (GGA+U) for this study. The calculation of total density of states (DOS) of TbNiSb shows that Ni-3d states dominate in valence band (VB) around -2 eV below fermi energy level (EF) in both spin-up and spin-down configurations, while spin up Tb-5d & spin down Tb- 4f states constitute the conduction band (CB) around 4 eV above the EF. We found a narrow energy gap 0.115 eV is opened showing the semiconducting nature of the TbNiSb compound. Tb –4f states lie around -8 eV below EF and not participate to the DOS near EF. We have also calculated the optical properties like dielectric constant, extinction coefficient, refractive index and reflectivity of TbNiSb compound.

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Bortoluzzi, Marco, Valentina Ferraro e Federica Sartor. "Photoluminescence of Homoleptic Lanthanide Complexes With Tris(benzotriazol-1-yl)borate". Journal of Fluorescence 31, n. 5 (13 luglio 2021): 1433–43. http://dx.doi.org/10.1007/s10895-021-02772-7.

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AbstractBright photoluminescent neutral complexes having general formula [Ln(tbtz)3] (Ln = Eu, Tb; tbtz = tris(benzotriazol-1-yl)borate) were obtained by reacting K[tbtz] with EuCl3 and TbCl3. The emissions in the visible range, related to the f-f transitions of the trivalent lanthanide ions, are observable upon excitation with wavelengths shorter than 350 nm. The most intense emission bands correspond to the 5D0 → 7F4 transition at 699 nm for the europium complex and to the 5D4 → 7F5 transition at 542 nm for the terbium derivative. The luminescence is in all the cases mostly associated with the antenna-effect from the coordinated tbtz ligands. The synthetic approach was successfully extended to the preparation of the analogous yttrium and gadolinium derivatives. Tricapped trigonal prismatic geometry was attributed to the complexes on the basis of luminescence data and DFT calculations. Highly photoluminescent plastic materials were obtained by embedding small amounts of [Eu(tbtz)3] or [Tb(tbtz)3] in poly(methyl methacrylate).

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Govindasamy, Anbu, Senthil Kumar Gopal, Saminathan Murugavel e Sekar Karuppannan. "Synthesis, crystal structure, density functional theory, drug-likeness, and molecular docking studies of a new carbazole-pyrazole derivative: A potential inhibitor of tuberculosis". INDIAN JOURNAL OF HETEROCYCLIC CHEMISTRY 34, n. 03 (settembre 2024): 335. http://dx.doi.org/10.59467/ijhc.2024.34.335.

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In this study, a compound combining a carbazole moiety with a pyrazole ring (4E)-4-((9-ethyl-9H-carbazol-3-yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one was synthesized and evaluated for its potential as an effective tuberculosis (TB) inhibitor. Compound 3 was synthesized by the condensation of 9-ethylcarbazole-3-carbaldehyde (1) with 4-amino-1,2-dihydro-2,3-dimethyl-1-phenyl-1H-pyrazol-5-one (2), and its 3D pose was employed by X-ray crystallography. The crystal structure analysis revealed the precise arrangement of atoms and provided insights into the compound's three-dimensional arrangement, which is crucial for understanding its interactions with biological targets. To assess the compound's pharmacokinetic properties and potential toxicity, an absorption, distribution, metabolism, excretion, and toxicity study was implemented. The results indicated satisfactory bioavailability and showed limited toxicity risks, suggesting a favorable safety profile. To gain insights into the compound's binding interactions of the compound with the target protein involved in TB, molecular docking studies were carried out. The docking results supported its potential as a TB inhibitor by highlighting its ability to establish favorable interactions within the binding pocket.. KEYWORDS :ADMET, Carbazole cum pyrazole, Crystal structure, DFT, Docking, Drug-likeness.

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Bentayeb, A., F. Driss Khodja, S. Chibani, N. Marbouh, B. Bekki, B. Khalfallah e M. Elkeurti. "Structural, electronic, and optical properties of AlNxSb1−x alloys through TB–mBJ–PBEsol: DFT study". Journal of Computational Electronics 18, n. 3 (4 maggio 2019): 791–801. http://dx.doi.org/10.1007/s10825-019-01338-y.

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El Amine Monir, Mohammed, Hadj Baltach, Ibtisam F. Al-Maaitah, A. F. Al-Maaitah, M. A. Ghebouli, M. Fatmi, Munirah D. Albaqami, Saikh Mohammad, Mourad Debbichi e Mika Sillanpää. "Half-metallic ferromagnetic features of V-doped Cu2O alloys: TB-mBJ and DFT + U insights". Results in Physics 57 (febbraio 2024): 107368. http://dx.doi.org/10.1016/j.rinp.2024.107368.

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Champagne, Aurélie, Samuel Dechamps, Simon M. M. Dubois, Aurélien Lherbier, Viet-Hung Nguyen e Jean-Christophe Charlier. "Computational Atomistic Modeling in Carbon Flatland and Other 2D Nanomaterials". Applied Sciences 10, n. 5 (3 marzo 2020): 1724. http://dx.doi.org/10.3390/app10051724.

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As in many countries, the rise of nanosciences in Belgium has been triggered in the eighties in the one hand, by the development of scanning tunneling and atomic force microscopes offering an unprecedented possibility to visualize and manipulate the atoms, and in the other hand, by the synthesis of nano-objects in particular carbon nanostructures such as fullerene and nanotubes. Concomitantly, the increasing calculating power and the emergence of computing facilities together with the development of DFT-based ab initio softwares have brought to nanosciences field powerful simulation tools to analyse and predict properties of nano-objects. Starting with 0D and 1D nanostructures, the floor is now occupied by the 2D materials with graphene being the bow of this 2D ship. In this review article, some specific examples of 2D systems has been chosen to illustrate how not only density functional theory (DFT) but also tight-binding (TB) techniques can be daily used to investigate theoretically the electronic, phononic, magnetic, and transport properties of these atomically thin layered materials.

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Haghdadi, Mina, e Nahid Farokhi. "Density functional theory (DFT) calculations of conformational energies and interconversion pathways in 1,2,7-thiadiazepane". Journal of the Serbian Chemical Society 76, n. 3 (2011): 395–406. http://dx.doi.org/10.2298/jsc100812040h.

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The molecular structure and conformational analysis of 1,2,7-thiadiazapane conformers were investigated by density functional theory (DFT) calculations at the B3LYP/cc-pVDZ level of theory. Four twist-chair (TC), six twist-boat (TB), two boat (B), two chair (C) and four twist (T) conformers were identified as minima and transition states for 1,2,7-thiadiazepane. The TC1 conformer is the most stable conformer and the twist-chair conformers are predicted to be lower in energy than their corresponding boat and chair conformations. DFT predicts a small barrier to pseudo-rotation and a remarkable activation barrier for the conformational interconversion of the twist-chair conformers to their corresponding boat conformers. The simplest conformational process and the one with the lowest barrier is the degenerate interconversion of the twist-chair 3 (TC3) conformation with itself via the CS symmetric chair (C2) transition state. The calculated strain energy barrier for this process is 2.41 kJ mol-1. The highest conformational interconversion barrier is between TC2 and twistboat 3 (TB3) forms, which was found to be 75.62 kJ mol-1.

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Chen, Huicong, e Jun Song. "Computational assessment of solute segregation at twin boundaries in magnesium: A two-factor model and solute effect on strengthening". Journal of Applied Physics 132, n. 22 (14 dicembre 2022): 225102. http://dx.doi.org/10.1063/5.0127266.

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This work presents a comprehensive first-principles density functional theory (DFT) study of solute segregation at [Formula: see text] and [Formula: see text] twin boundaries (TBs) in Mg. A total of 56 solute elements were investigated. For each solute element, the preferential segregation sites at two TBs were identified and the associated segregation energies were computed. A two-factor model that considers both lattice strain and electronegativity, representing the mechanical and chemical effects respectively, has been proposed to predict the solute segregation energy. The model prediction shows good agreement with the DFT calculation. It was found that the mechanical effect dominates the solute segregation energy. However, depending on the site of segregation, the chemical effect can become sizable to warrant consideration. The degree of solute segregation at TBs at different temperatures was then quantified by calculating the solute concentration at TBs at different temperatures. The effect of solutes in either strengthening or weakening the TB was also evaluated. The results provide a basis for selecting promising solutes in the development of new high-performance Mg alloys.

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Reshak, A. H. "Revealing the transport properties of the spin-polarized β′-Tb 2 (MoO 4 ) 3 : DFT+U". Journal of Magnetism and Magnetic Materials 441 (novembre 2017): 124–30. http://dx.doi.org/10.1016/j.jmmm.2017.05.060.

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Oyarzabal, Itziar, Estitxu Echenique-Errandonea, Eider San Sebastián, Antonio Rodríguez-Diéguez, José Manuel Seco e Enrique Colacio. "Synthesis, Structural Features and Physical Properties of a Family of Triply Bridged Dinuclear 3d-4f Complexes". Magnetochemistry 7, n. 2 (5 febbraio 2021): 22. http://dx.doi.org/10.3390/magnetochemistry7020022.

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New dinuclear MII-LnIII complexes of general formulas [Cu(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN·H2O (LnIII = Gd (1), Tb (2), Dy (3) and Er (4)), [Ni(CH3CN)(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN (LnIII = Nd (5), Gd (6), Tb (7), Dy (8), Er (9) and Y (10)) and [Co(CH3CN)(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN (LnIII = Gd (11), Tb (12), Dy (13), Er (14) and Y (15)) were prepared from the compartmental ligand N,N′-dimethyl-N,N′-bis(2-hydroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H2L). In all these complexes, the transition metal ions occupy the internal N2O2 coordination site of the ligand, whereas the LnIII ions lie in the O4 external site. Both metallic ions are connected by an acetate bridge, giving rise to triple mixed diphenoxido/acetate bridged MIILnIII compounds. Direct current (dc) magnetic measurements allow the study of the magnetic exchange interactions between the 3d and 4f metal ions, which is supported by density functional theory (DFT) theoretical calculations for the GdIII-based counterparts. Due to the weak ferromagnetic exchange coupling constants obtained both experimentally and theoretically, the magneto-thermal properties of the less anisotropic systems (compounds 1 and 6) are also studied. Alternating current (ac)magnetic measurements reveal the occurrence of slight frequency dependency of the out-of-phase signal for complexes 8, 9 and 13, while complex 15 displays well-defined maximums below ~6 K.

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Deylgat, Emeric, Sabyasachi Tiwari, William G. Vandenberghe e Bart Sorée. "Impact of passivation on the Dirac cones of 2D topological insulators". Journal of Applied Physics 131, n. 23 (21 giugno 2022): 235101. http://dx.doi.org/10.1063/5.0094246.

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Topological insulators have unique properties that make them promising materials for future implementation in next-generation electronic devices. However, topological insulators like stanene nanoribbons need to be passivated before they can be used in devices. We calculate the electronic band structure of stanene nanoribbons (SNRs) that are passivated by hydrogen (H), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or sodium (Na). We show that the difference between the electronegativity of the passivation material and the tin atoms defines the position of the Dirac cone of the topological insulator edge states. We develop a four-parameter tight-binding model based on the Kane–Mele model [Kane and Mele, Phys. Rev. Lett. 95, 226801 (2005); Kane and Mele, Phys. Rev. Lett. 95, 146802 (2005)]. The hopping parameters of the TB model are obtained by fitting the tight-binding model to the density functional theory (DFT) calculations. Finally, we demonstrate that the DFT band structures and the tight-binding model band structures are in good agreement with each other at low energies around the Dirac point, thereby capturing the complete physics of the passivated edge bands.

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Toader, Ana Maria, Bogdan Frecus, Corneliu Ioan Oprea e Maria Cristina Buta. "Assessing Quantum Calculation Methods for the Account of Ligand Field in Lanthanide Compounds". Physchem 3, n. 2 (16 giugno 2023): 270–89. http://dx.doi.org/10.3390/physchem3020019.

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We obtained thorough insight into the capabilities of various computational methods to account for the ligand field (LF) regime in lanthanide compounds, namely, a weakly perturbed ionic body and quasidegenerate orbital multiplets. The LF version of the angular overlap model (AOM) was considered. We intentionally took very simple idealized systems, the hypothetical [TbF]2+, [TbF2]+ and [Tb(O2NO)]2+, in order to explore the details overlooked in applications on complex realistic systems. We examined the 4f and 5d orbital functions in connection to f–f and f–d transitions in the frame of the two large classes of quantum chemical methods: wave function theory (WFT) and density functional theory (DFT). WFT methods are better suited to the LF paradigm. In lanthanide compounds, DFT faces intrinsic limitations because of the frequent occurrence of quasidegenerate ground states. Such difficulties can be partly encompassed by the nonstandard control of orbital occupation schemes. Surprisingly, we found that the simplest crystal field electrostatic approximation, reconsidered with modern basis sets, works well for LF parameters in ionic lanthanide systems. We debated the largely overlooked holohedrization effect that inserts artificial inversion symmetry into standard LF Hamiltonians.

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Reyes, Yves Ira A., e Francisco C. Franco. "DFT study on the effect of proximal residues on the Mycobacterium tuberculosis catalase-peroxidase (katG) heme compound I intermediate and its bonding interaction with isoniazid". Physical Chemistry Chemical Physics 21, n. 30 (2019): 16515–25. http://dx.doi.org/10.1039/c9cp01465a.

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In M. tb. katG heme CpdI intermediate, an electron transfer from the π-orbital of the residue, Trp321, to the a_2u-orbital of porphyrin ring, results in a radical character for Trp321, resulting in a stronger H-bonding interaction with INH.

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31

Mandal, Supantha, Utsa Das, Dipali Nayak, Sayantan Bakshi e Buddhadev Pradhan. "Investigation of electronic and optical properties of PbxSn1-xO2 for optoelectronic applications: A TB-mBJ DFT approach". Computational Condensed Matter 31 (giugno 2022): e00691. http://dx.doi.org/10.1016/j.cocom.2022.e00691.

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32

HAMLAT, Mama. "Enhancement of the magneto-electronic properties by GGA and TB-mBJ approaches for KMgO3 perovskite oxide". Physics of Semiconductor Devices & Renewable Energies Journal 1, n. 1 (9 luglio 2024): 08. http://dx.doi.org/10.59684/psdrej.v1i1.8.

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We investigate the structural, elastic, electronic and magnetic properties of KMgO3. First-principal calculations, based on the formalism of the density functional theory (DFT) and the method of full potential augmented and linearized plane waves (FP-LAPW) implemented in the Wien2k code. The exchange and correlation effects were treated by the following two approximations: generalized gradient approximation (GGA) and Tran-Blaha modified beck Johnson (TB-mBJ) potentials. After analyzing the obtained structural parameters, the results revealed that KMgO3compound is most stable in its ferromagnetic configuration. The formation energy value showed that this compound can be experimentally synthesized. Furthermore, the calculated band structures, and density of states (DOSs) indicate the half-metallic behavior of KMgO3. We found also that the total magnetic moment is an integer value of 3μBwhich confirms the half-metallic character. The magnetic moment specially issues from the spin-polarization of p electrons of O atoms.

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Kumar, Sachin, Naven Kumar, Kamna Yadav e R. P. Singh. "DFT study of optoelectronic spectra of barium cadmium chalcogenides (Ba2CdX3, X = S, Se and Te)". Materials Science-Poland 37, n. 3 (1 settembre 2019): 417–25. http://dx.doi.org/10.2478/msp-2019-0045.

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AbstractDFT analyses of electronic and optical spectra of barium cadmium chalcogenides (Ba2CdX3, X = S, Se, Te) have been carried out. The study of electronic spectra has been made in terms of band structure and density of states using full potential linear augmented plane wave plus local orbital method. Band structure calculations have been carried out under the approximations PBE-GGA, PBE-Sol, LDA and TB-mBJ. Band structures of these materials show that Ba2CdS3, Ba2CdSe3 and Ba2CdTe3 crystals possess a band gap less than 1 eV, underestimated relative to the experimental/theoretical literature values. Optical spectra of these chalcogenides have been analyzed in terms of real and imaginary parts of dielectric function, reflectivity, refractive index, extinction coefficient, absorption coefficient, optical conductivity and electron energy loss. Optical results show large anisotropy along different directions. These results provide a physical basis of barium cadmium chalcogenides for potential application in optoelectronic devices.

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Kharwar, Ajit Kumar, Arpan Mondal e Sanjit Konar. "Field Induced Slow Magnetic Relaxation in a Non Kramers Tb(III) Based Single Chain Magnet". Magnetochemistry 4, n. 4 (19 dicembre 2018): 59. http://dx.doi.org/10.3390/magnetochemistry4040059.

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Herein, we report a novel Tb(III) single chain magnet with the chemical formulae [Tb(μ-OH2)(phen)(μ-OH)(nb)2]n by using 4-nitrobenzoic acid (Hnb) and 1,10-phenanthroline (phen) as ligand system. The single-crystal X-ray diffraction reveals that 4-nitrobenzoic acid acts as a monodentate ligand, water and hydroxyl ions are the bridging ligand and the phen serves as a bidentate chelating ligand. The static magnetic susceptibility measurement (from 2 K to 300 K) shows ferromagnetic interaction at very low temperature (below 6 K). The alternating current (AC) susceptibility data of the complex show temperature and frequency dependence under an applied 2000 Oe DC (direct current) field. The phen moiety behaves as an antenna and enables the complex to show the green light fluorescence emission by absorption-energy transfer-emission mechanism. To calculate the exchange interaction, broken symmetry density functional theory (BS-DFT) calculations have been performed on a model compound which also reveals weak ferromagnetic interaction. Ab initio calculations reveals the anisotropic nature (gz = 15.8, gy, gy = 0) of the metal centre and the quasi doublet nature of ground state with small energy gap and that is well separated from the next excited energy state.

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Simserides, Constantinos, Andreas Morphis e Konstantinos Lambropoulos. "Hole Transfer in Open Carbynes". Materials 13, n. 18 (8 settembre 2020): 3979. http://dx.doi.org/10.3390/ma13183979.

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We investigate hole transfer in open carbynes, i.e., carbon atomic nanowires, using Real-Time Time-Dependent Density Functional Theory (RT-TDDFT). The nanowire is made of N carbon atoms. We use the functional B3LYP and the basis sets 3-21G, 6-31G*, cc-pVDZ, cc-pVTZ, cc-pVQZ. We also utilize a few Tight-Binding (TB) wire models, a very simple model with all sites equivalent and transfer integrals given by the Harrison ppπ expression (TBI) as well as a model with modified initial and final sites (TBImod) to take into account the presence of one or two or three hydrogen atoms at the edge sites. To achieve similar site occupations in cumulenes with those obtained by converged RT-TDDFT, TBImod is sufficient. However, to achieve similar frequency content of charge and dipole moment oscillations and similar coherent transfer rates, the TBImod transfer integrals have to be multiplied by a factor of four (TBImodt4times). An explanation for this is given. Full geometry optimization at the B3LYP/6-31G* level of theory shows that in cumulenes bond length alternation (BLA) is not strictly zero and is not constant, although it is symmetrical relative to the molecule center. BLA in cumulenic cases is much smaller than in polyynic cases, so, although not strictly, the separation to cumulenes and polyynes, approximately, holds. Vibrational analysis confirms that for N even all cumulenes with coplanar methylene end groups are stable, for N odd all cumulenes with perpendicular methylene end groups are stable, and the number of hydrogen atoms at the end groups is clearly seen in all cumulenic and polyynic cases. We calculate and discuss the Density Functional Theory (DFT) ground state energy of neutral molecules, the CDFT (Constrained DFT) “ground state energy” of molecules with a hole at one end group, energy spectra, density of states, energy gap, charge and dipole moment oscillations, mean over time probabilities to find the hole at each site, coherent transfer rates, and frequency content, in general. We also compare RT-TDDFT with TB results.

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Li, An, Xi Chen, Guanjun Gao e William Shieh. "Transmission of 1 Tb/s Unique-Word DFT-Spread OFDM Superchannel Over 8000 km EDFA-Only SSMF Link". Journal of Lightwave Technology 30, n. 24 (dicembre 2012): 3931–37. http://dx.doi.org/10.1109/jlt.2012.2206369.

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37

Yazdanmehr, M., S. Jalali-Asadabadi, J. Nematollahi, A. Nourmohammadi e Iftikhar Ahmad. "Predictions of bandgap and subbands of γ−Al2O3 in presence of intrinsic point defects by DFT+TB-mBJ". Computational Condensed Matter 19 (giugno 2019): e00379. http://dx.doi.org/10.1016/j.cocom.2019.e00379.

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38

Takassa, Rabi, Omar Farkad, El Alami Ibnouelghazi e Driss Abouelaoualim. "Electronic Properties and Band Gaps of Single-Wall Carbon Nanotubes Using <i>π</i> Orbitals Tight-Binding Model: A Comparative Study with <i>Ab Initio</i> Density Functional Theory". Journal of Nano Research 74 (12 luglio 2022): 1–10. http://dx.doi.org/10.4028/p-85523u.

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Abstract (sommario):

Semiconducting single-wall carbon nanotubes (SWCNTs) have already emerged as a promising candidate for molecular electronics and photovoltaic applications including solar cells. Any application of semiconducting SWCNTs is primarily related to proper information about its bandgap. In this work, the impact of the chirality indices and diameters of a series of armchair and zigzag SWCNTs on the electronic properties (band gap, electronic band structure and density of states (DOS)) are investigated using semi-empirical π orbitals tight-binding (TB) method. The results indicate that the electronic behaviour of the nanotubes changes according to chirality, the total number of electronic sub-bands gets increased when the chirality increases and Van Hove singularities (VHs) appear in its electronic DOS. We have found that for small diameter tubes (less than 0.8 nm), the calculated band gaps don’t agree with DFT calculations based on ab-initio (LDA and GGA) methods, which shows that the semi-empirical TB method including π orbitals only is not sufficient to give a reasonable description of small nanotubes. All Obtained results are in good agreement with previous studies. Semiconducting SWCNTs used in this study are particularly well-suited for the nanoelectronic devices and optoelectronic applications with their direct bandgap and optical transitions, while metallic SWCNTs are considered to be ideal candidates for variety of future nanoelectronic applications such as nanocircuit interconnects and power transmission cables.

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Grebenyuk, Dimitry, Mirijam Zobel e Dmitry Tsymbarenko. "Partially Ordered Lanthanide Carboxylates with a Highly Adaptable 1D Polymeric Structure". Polymers 14, n. 16 (16 agosto 2022): 3328. http://dx.doi.org/10.3390/polym14163328.

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A new family of 14 isostructural [Ln(piv)3(en)]∞ lanthanide pivalate (piv−, 2,2-dimethylpropanoate) complexes with ethylenediamine (en) was synthesized by a topology-preserving transformation from 1D coordination polymers [Ln(piv)3]∞. The crystal structures of the compounds were determined by single-crystal and powder X-ray diffraction, which demonstrated that despite the regular ligand arrangement within the chains, the latter are intricately packed within the partially ordered crystal, as only two of four ligands are strictly bound by the translational symmetry. The peculiarities of the lanthanide coordination environment were explored by total X-ray scattering with pair distribution function analysis. Periodic DFT calculations revealed the chain stabilization by intrachain H-bonds and weak interchain interactions. Noticeably, the energy difference was infinitesimally small even between the two considered extreme variants of ordered packing, which is in line with the disturbed packing order of the chains. The luminescent properties of Eu and Tb complexes were investigated in order to prove the energy transfer between lanthanide ions within the heterometallic complex. This opens up the prospect of creating new materials for optical applications. The heterometallic compound Eu0.05Tb0.95(piv)3(en) was synthesized, and was found to demonstrate temperature-dependent luminescence with a linear dependence of the thermometric parameter I(Eu)/I(Tb) within the temperature range from −80 °C to 80 °C, and had a maximum relative sensitivity value of 0.2%/K.

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Carrasco, Fernando, Wilfredo Hernández, Oscar Chupayo, Patricia Sheen, Mirko Zimic, Jorge Coronel, Celedonio M. Álvarez et al. "Phenylisoxazole-3/5-Carbaldehyde Isonicotinylhydrazone Derivatives: Synthesis, Characterization, and Antitubercular Activity". Journal of Chemistry 2021 (31 ottobre 2021): 1–14. http://dx.doi.org/10.1155/2021/6014093.

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Eight new phenylisoxazole isoniazid derivatives, 3-(2′-fluorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (1), 3-(2′-methoxyphenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (2), 3-(2′-chlorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (3), 3-(3′-clorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (4), 3-(4′-bromophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (5), 5-(4′-methoxiphenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (6), 5-(4′-methylphenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (7), and 5-(4′-clorophenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (8), have been synthesized and characterized by FT-IR, 1H-NMR, 13C-NMR, and mass spectral data. The 2D NMR (1H-1H NOESY) analysis of 1 and 2 confirmed that these compounds in acetone-d6 are in the trans(E) isomeric form. This evidence is supported by computational calculations which were performed for compounds 1–8, using DFT/B3LYP level with the 6-311++G(d,p) basis set. The in vitro antituberculous activity of all the synthesized compounds was determined against the Mycobacterium tuberculosis standard strains: sensitive H37Rv (ATCC-27294) and resistant TB DM97. All the compounds exhibited moderate bioactivity (MIC = 0.34–0.41 μM) with respect to the isoniazid drug (MIC = 0.91 μM) against the H37Rv sensitive strain. Compounds 6 (X = 4′-OCH3) and 7 (X = 4′-CH3) with MIC values of 12.41 and 13.06 μM, respectively, were about two times more cytotoxic, compared with isoniazid, against the resistant strain TB DM97.

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Balodhi, Ashiwini, James Torres, Rinkle Juneja, Kelvin B. Chang, Allen Brady, Sunil K. Chakrapani, Lucas R. Lindsay, Raphael P. Hermann e Alexandra Zevalkink. "Determination of single-crystal elastic moduli of LiREF₄ (RE = Y, Gd, and Tb) by resonant ultrasound spectroscopy". Journal of Applied Physics 132, n. 17 (7 novembre 2022): 175110. http://dx.doi.org/10.1063/5.0109940.

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The tetragonal fluoro-scheelite [Formula: see text] compounds ([Formula: see text]) have been shown to exhibit a variety of useful optical and magnetic properties. While [Formula: see text] has been widely studied, many of the fundamental thermodynamic properties of other members of this family remain unknown. Here, we report the complete elastic tensors ([Formula: see text]) of single-crystalline [Formula: see text], [Formula: see text], and [Formula: see text] using resonant ultrasound spectroscopy and density functional theory (DFT). We compare the results for [Formula: see text] with prior experimental results using time-of-flight ultrasound methods. This is the first report, however, of the experimental elastic tensors of [Formula: see text] and [Formula: see text]. The present results point to a softening of the elastic moduli of the [Formula: see text] system when Y is replaced by the larger ionic radius of Tb or Gd. Furthermore, we find that just 0.3% doping with Nd on the Y site also leads to a slight softening of the moduli. The variation of the elastic moduli as a function of temperature up to [Formula: see text] was also measured. A nearly linear softening of all seven independent elastic moduli was observed with increasing temperature. Phonon dispersions and phonon density of states obtained by DFT support the experimental finding of a significantly higher sound velocity due to lighter Y atoms in [Formula: see text], as compared to heavier [Formula: see text] and [Formula: see text].

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Shyichuk, Andrii, Marcin Runowski, Stefan Lis, Jakub Kaczkowski e Andrzej Jezierski. "Semiempirical and DFT computations of the influence of Tb(III) dopant on unit cell dimensions of cerium(III) fluoride". Journal of Computational Chemistry 36, n. 3 (18 novembre 2014): 193–99. http://dx.doi.org/10.1002/jcc.23789.

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43

Amrani, S., M. Berber e M. Mebrek. "DFT based investigation of the structural, magnetic, electronic, and half-metallic properties of solid In1-xTixSb solutions". Condensed Matter Physics 24, n. 4 (2021): 43704. http://dx.doi.org/10.5488/cmp.24.43704.

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With the intention to reveal the effect of the substitution, Ti-doped InSb alloy, we accomplished a first-principles prediction within the FPLAPW+lo method. We used GGA-PBEsol scheme attached with the improved TB-mBJ approach to predict structural, electronic, and magnetic properties of In1-xTixSb with concentration x=0, 0.125, 0.25, 0.50, 0.75, 0.875, and 1. Our lattice parameters are found in favorable agreement with the available theoretical and experimental data. The calculation shows that all structures are energetically stable. The substitutional doping transforms the ionic character of the InSb compound in half-metallic ferromagnetic comportment for concentration x = 0, 0.125, 0.25, and 0.50, with a spin polarization of 100% at the Fermi level, and metallic nature for In0.25Ti0.75Sb and In0.125Ti0.875Sb. The total magnetic moments are also estimated at about 1 mu;B. In0.875Ti0.125Sb, In0.75Ti0.25Sb, and In0.50Ti0.50Sb have half-metallic ferromagnets comportment and they can be upcoming applicants for spintronics applications.

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Chatta, Wahiba, Brahim Lagoun, Hamza Lidjici, Abdelhakim Chadli, Abderrahmane Cheriet, Hichem Farh, Hamadi Khemakhem e Khenchoul Salah. "TB-mBJ Calculations of Structural and Optoelectronic Properties of the Rhombohedral Phase of Bismuth Sodium Titanate (Bi_0.5 Na_0.5)TiO₃". Solid State Phenomena 297 (settembre 2019): 165–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.297.165.

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In the present work, we report an ab initio investigation of the structural, electronic and linear optical properties of (Na0.5Bi0.5)TiO3 (NBT) in its rhombohedral phase, using a Full Potential Augmented Plane Waves (FP-LAPW) method in the frame work of Density Functional Theory (DFT) with the TB-mBJ potential for a better description of the electronic properties. Firstly a Full structure optimization was performed with a relaxation of atomics positions to minimize the Hellmann-Feynman forces exerted over the atoms. The calculated lattice parameters of the rhombohedral phase of NBT are in very good agreement with experimental values with a deviation of 0.9%. The electronic density of states are presented and commented. The calculated band structure shows that our compound has an indirect band gap of 3.30eV. Furthermore, the optical properties were presented, compared with experimental ones present in the literature and commented.

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Barzdajn, Bartosz, Alexander M. Garrett, Thomas M. Whiting e Christopher P. Race. "Development of data-driven spd tight-binding models of Fe—parameterisation based on QSGW and DFT calculations including information about higher-order elastic constants". Modelling and Simulation in Materials Science and Engineering 29, n. 8 (20 ottobre 2021): 085006. http://dx.doi.org/10.1088/1361-651x/ac2b31.

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Abstract Quantum-mechanical (QM) simulations, thanks to their predictive power, can provide significant insights into the nature and dynamics of defects such as vacancies, dislocations and grain boundaries. These considerations are essential in the context of the development of reliable, inexpensive and environmentally friendly alloys. However, despite significant progress in computer performance, QM simulations of defects are still extremely time-consuming with ab-initio/non-parametric methods. The two-centre Slater–Koster (SK) tight-binding (TB) models can achieve significant computational efficiency and provide an interpretable picture of the electronic structure. In some cases, this makes TB a compelling alternative to models based on abstraction of the electronic structure, such as the embedded atom model. The biggest challenge in the implementation of the SK method is the estimation of the optimal and transferable parameters that are used to construct the Hamiltonian matrix. In this paper, we will present results of the development of a data-driven framework, following the classical approach of adjusting parameters in order to recreate properties that can be measured or estimated using ab-initio or non-parametric methods. Distinct features include incorporation of data from QSGW (quasi-particle self-consistent GW approximation) calculations, as well as consideration of higher-order elastic constants. Furthermore, we provide a description of the optimisation procedure, omitted in many publications, including the design stage. We also apply modern optimisation techniques that allow us to minimise constraints on the parameter space. In summary, this paper introduces some methodological improvements to the semi-empirical approach while addressing associated challenges and advantages.

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Ibrir, Miloud. "Structural, electronic and thermoelectric properties of the intermetallic materials based on Mg2X (X= Si, Ge, Sn): DFT calculations". International Journal of Energetica 2, n. 2 (31 dicembre 2017): 25. http://dx.doi.org/10.47238/ijeca.v2i2.44.

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The scope of this work is the investigation of the physical properties of chalcopyrite materials using ab-initio methods in order to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. In the first framework, we obtained the results of calculations based on Density Functional Theory (DFT) using the full-potential linearized augmented plane wave method (FP-LAPW) as involved in the WIEN2K computational package. For the exchange-correlation potential, the local density approximation (LDA) was used to calculate the lattice parameters, Bulk modulus and its first derivative as well as the densities of states of the intermetallic semiconductors materials based on Mg2X (X=Si, Ge and Sn). The semi-local Becke-Johnson (mBJ) potential and its modified form proposed by Tran and Blaha (TB-mBJ) were also used for studying the electronic and thermoelectric properties; (merit factor, Seebeck coefficient, electronic conductivity). The achieved results were compared to computational works and other data acquired experimentally.

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Sihem, Filalli, e Hamdad Noura. "Optimizing Configurations for Determining the Electromagnetic Properties of CsFeF3, NaFeF3, and RbFeF3 Fluorides: GGA vs GGA+U and TB-mBj Approaches". Annals of West University of Timisoara - Physics 62, n. 1 (1 dicembre 2020): 71–94. http://dx.doi.org/10.2478/awutp-2020-0005.

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AbstractThe structural, electronic and magnetic properties of (Cubic Pm-3m, Hexagonal-4H, orthorhombic Pnma, and orthorhombic Pbnm) phases of AFeF3 Fluorides (A = Cs, Na, and Rb) are reported theoretically using full potential linearized augmented plane waves method within the density functional theory (DFT). Using different exchange–correlation approximations including the generalized gradient approximation (PBE-GGA, WC-GGA, and PBEsol-GGA), also (GGA) with Hubbard potential (GGA + U) and The modified Becke Johnson potential (mBJ), we carried to determine various physical properties. The Calculations revealing that the estimated structural parameters are reliable with the experimentally reported data. Magnetically all these intermetallics are Ferromagnetic (FM). The ground-state energy of different magnetic phases studied showed that the magnetic moments are evaluated per atom, and overestimated by (GGA+U). Transfer charge reveals a strong covalent interaction between Fe-Fe atoms. Their electronic band structure and density of states indicate insulator behavior.

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Annveer, Rahul Gauram, Rishi P. Singh, Arvind Kumar VERMA e Praveen Kumar. "Study of Magnetic, Optical, Electronic and Thermodynamic Effects in Thallium Rare Earth Disulphides (TlRES2, RE= Tb- Er)". Materials Plus 2, n. 1 (16 giugno 2023): 20–34. http://dx.doi.org/10.37256/mp.2120232857.

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In the present research work, we have investigated density of electronic states, electronic band structure, magnetic structure, optical spectra and temperature dependent thermodynamic characteristics of thallium rare earth sulphides, TlRES2 (RE: Tb-Er) using FP-LAPW method and PBE-GGA exchange correlation within DFT. The electronic structure pointed out that TlRES2 compounds show half metallic character. The magnetic moment and spin polarization calculations prove that TlRES2 are fully spin polarized compounds with ferromagnetic nature. Optical spectra show that intraband transitions occur in infrared (IR) regime due to half metallic character of TlRES2 and behave as opaque in ultraviolet (UV) region. High refractive index in IR regime also show metallic character and high peak in UV regime show slow propagation of light in UV regime. The reflection coefficient is found maximum (~50–60%) in UV regime. Greater energy loss has been seen on the higher energy side, which corresponds to the stimulation of plasmons by electrons moving through the compounds. Plasma resonances lead to the frequent peaks at ~ 6.0 eV, 11.0 eV, and 12.0 eV. According to calculations made using the quasi-harmonic Debye model, TlRES2 compounds are dimensionally less stable (i.e., much hard), have poor thermal conductivity, and experience faster-than-average disorder with increasing the temperature.

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Burnett, Logan, Matthew P. Clay, Yogesh K. Vohra e Cheng-Chien Chen. "First-Principles Calculation of Hubbard U for Terbium Metal under High Pressure". Journal of Physics: Condensed Matter, 15 luglio 2024. http://dx.doi.org/10.1088/1361-648x/ad6387.

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Abstract Using density functional theory (DFT) and linear response approaches, we compute the on-site Hubbard interaction $U$ of elemental Terbium (Tb) metal in the pressure range $\sim 0-65$ GPa. The resulting first-principles $U$ values with experimental crystal structures enable us to examine the magnetic properties of Tb using a DFT+U method. The lowest-energy magnetic states in our calculations for different high-pressure Tb phases -- including hcp, $\alpha$-Sm, and dhcp -- are found to be compatible with the corresponding magnetic ordering vectors reported in experiments. The result shows that the inclusion of Hubbard $U$ substantially improves the accuracy and efficiency in modeling correlated rare-earth materials. Our study also provides the necessary $U$ information for other quantum many-body techniques to study Tb under extreme pressure conditions.

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Poidevin, Corentin, Gwenhaël Duplaix-Rata, Karine Costuas e Arnaud Fihey. "Evaluation of tight-binding DFT performance for the description of organic photochromes properties". Journal of Chemical Physics, 2 febbraio 2023. http://dx.doi.org/10.1063/5.0133418.

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Photochrome molecules are widely studied for their many potential applications. It exists a considerable chemical space to explore for the optimization of the required properties and a necessity to understand their incorporation in devices. Thus, cheap and reliable computational methods can be powerful tools to steer synthetic developments. As DFT methods remain costly for any extensive studies, semi-empirical methods like Density Functional Tight-Binding (TB) could offer a good compromise between accuracy computational cost. However, these approaches necessitate benchmarking on the families of compounds of interest. Thus, the aim of the present study is to evaluate the accuracy of key features calculated with TB methods (DFTB2, DFTB3, GFN2-xTB, and LC-DFTB2) for three sets of photochromic molecules: azobenzene (AZO), norbornadiene/quadricyclane (NBD/QC) and dithienylethene (DTE) derivatives. The features considered are the optimized geometries, the difference in energy between the two isomers (ΔE), and the energies of the first relevant excited states. All the TB results are compared to those obtained with DFT methods and state-of-the-art electronic structure calculation methods: DLPNO-CCSD(T) for ground states and DLPNO-STEOM-CCSD for excited states. Our results show that, overall, DFTB3 is the TB method leading to the best results for the geometries and the ΔE values and can be use alone for these purposes for NBD/QC and DTE derivatives. Single point calculations using r2SCAN-3c with TB geometries allow circumvent the deficiencies of the TB methods in the AZO series. For the electronic transitions, the range-separated LC-DFTB2 method is the most accurate TB method tested for AZO and NBD/QC derivatives.

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