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Journal articles on the topic 'Correlated electron gas'

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Published: 4 June 2021
Last updated: 4 February 2022

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1

Saarela, M., T. Taipaleenm ki, and F. V. Kusmartsev. "Charged clusters in strongly correlated electron gas." Journal of Physics A: Mathematical and General 36, no. 35 (August 20, 2003): 9223–36. http://dx.doi.org/10.1088/0305-4470/36/35/309.

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2

Thakur, J. S., and D. Neilson. "Superconductivity in a correlated disordered two-dimensional electron gas." Physical Review B 58, no. 20 (November 15, 1998): 13717–20. http://dx.doi.org/10.1103/physrevb.58.13717.

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3

Zverev, M. V., V. A. Khodel, and S. S. Pankratov. "Microscopic theory of a strongly correlated two-dimensional electron gas." JETP Letters 96, no. 3 (October 2012): 192–202. http://dx.doi.org/10.1134/s0021364012150131.

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4

MACDONALD, A. H. "CORRELATIONS WEAK AND STRONG: DIVERS GUISES OF THE TWO-DIMENSIONAL ELECTRON GAS." International Journal of Modern Physics B 13, no. 05n06 (March 10, 1999): 447–59. http://dx.doi.org/10.1142/s0217979299000345.

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The three-dimensional electron-gas model has been a major focus for many-body theory applied to the electronic properties of metals and semiconductors. Because the model neglects band effects, whereas electronic systems are generally more strongly correlated in narrow band systems, it is most widely used to describe the qualitative physics of weakly correlated metals with unambiguous Fermi liquid properties. The model is more interesting in two space dimensions because it provides a quantitative description of electrons in quantum wells and because these can form strongly correlated many-particle states. We illustrate the range of possible many-particle behaviors by discussing the way correlations are manifested in 2D tunneling spectroscopy experiments.
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5

Heinzel, T., R. Jäggi, E. Ribeiro, M. v. Waldkirch, K. Ensslin, S. E. Ulloa, G. Medeiros-Ribeiro, and P. M. Petroff. "Transport signatures of correlated disorder in a two-dimensional electron gas." Europhysics Letters (EPL) 61, no. 5 (March 2003): 674–80. http://dx.doi.org/10.1209/epl/i2003-00129-8.

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6

Barbaro, M. B., A. De Pace, T. W. Donnelly, and A. Molinari. "Parity-violating electron scattering from the pion-correlated relativistic Fermi gas." Nuclear Physics A 569, no. 4 (March 1994): 701–31. http://dx.doi.org/10.1016/0375-9474(94)90381-6.

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7

Lederer, Pascal, and J. P. Rodriguez. "de Haas–van Alphen effect in a strongly correlated electron gas." Physical Review B 46, no. 2 (July 1, 1992): 1220–23. http://dx.doi.org/10.1103/physrevb.46.1220.

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8

Ioffe, L. B., D. Lidsky, and B. L. Altshuler. "Effective lowering of dimensionality in the strongly correlated two dimensional electron gas." Physical Review Letters 73, no. 3 (July 18, 1994): 472–75. http://dx.doi.org/10.1103/physrevlett.73.472.

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9

Continentino, M. A. "Scaling Theory of the Metal-Insulator Transition in the Highly Correlated Electron Gas." Europhysics Letters (EPL) 9, no. 1 (May 1, 1989): 77–82. http://dx.doi.org/10.1209/0295-5075/9/1/014.

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10

Buks, E., M. Heiblum, and Hadas Shtrikman. "Correlated charged donors and strong mobility enhancement in a two-dimensional electron gas." Physical Review B 49, no. 20 (May 15, 1994): 14790–93. http://dx.doi.org/10.1103/physrevb.49.14790.

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11

Kwong, N. H., and M. Bonitz. "Real-Time Kadanoff-Baym Approach to Plasma Oscillations in a Correlated Electron Gas." Physical Review Letters 84, no. 8 (February 21, 2000): 1768–71. http://dx.doi.org/10.1103/physrevlett.84.1768.

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12

Schlottmann, P. "Exact Results for Highly Correlated Electron Systems in One Dimension." International Journal of Modern Physics B 11, no. 04n05 (February 20, 1997): 355–667. http://dx.doi.org/10.1142/s0217979297000368.

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One-dimensional conductors are a long-standing topic of research with direct applications to organic conductors and mesoscopic rings. The discovery of the ceramic high-temperature superconductors has revitalized the interest in low-dimensional charge and spin fluctuations of highly correlated electron systems. Several mechanisms proposed to explain the high-T c superconductors invoke properties of the two-dimensional Hubbard model, but probably also some one-dimensional aspects are relevant. Numerous one-dimensional models for correlated electrons have been studied with various approximate, asymptotically exact and exact methods. These results lead to the concept of Luttinger liquid for interacting electron gases without excitation gaps (metallic systems). Characteristic of Luttinger liquids are the charge and spin separation, marginal Fermi liquid properties, e.g. the absence of quasiparticles in the vicinity of the Fermi surface, nonuniversal power-law singularities in the one-particle spectral function and the related absence of a discontinuity in the momentum distribution at the Fermi level, the power-law decay of correlation functions for long times and large distances, persistent currents in finite rings, etc. Due to the peculiarities of the phase space in one dimension some of the models have sufficient conserved currents to be completely integrable. We review exact results derived within the framework of Bethe's ansatz for integrable one-dimensional models of correlated electrons. The Bethe-ansatz method is presented by explicitly showing the steps leading to the solution of the N-component electron gas interacting via a δ-function potential (repulsive and attractive interaction), which is probably the simplest model of correlated electrons. Emphasis is given to the procedure to extract the groundstate properties, the classification of states, the excitation spectrum, the thermodynamics and finite size effects, such as critical exponents of correlation functions and persistent currents. The method is then applied to numerous other models, e.g. (i) a two-band model involving attractive and repulsive potentials and crystalline fields splitting the bands, (ii) the traditional Hubbard chain with attractive and repulsive U, (iii) the degenerate Hubbard model with repulsive U, which displays a metal–insulator transition at a finite U, (iv) a two-band Hubbard model with repulsive U, (v) the traditional supersymmetric t–J model (vi) a two-band supersymmetric t–J model with band-splitting and (vii) the N-component supersymmetric t–J model. Finally, results for models with long-range interactions, in particular r-2 and sinh -2(r) potentials, are briefly reviewed.
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13

Gold, A., and L. Calmels. "Spin-susceptibility and spin-density excitations in the correlated quasi-one-dimensional electron gas." Physica E: Low-dimensional Systems and Nanostructures 2, no. 1-4 (July 1998): 426–30. http://dx.doi.org/10.1016/s1386-9477(98)00088-5.

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14

Johnson, Neil F., and Luis Quiroga. "Microscopic analytical theory of a correlated, two-dimensionalN-electron gas in a magnetic field." Journal of Physics: Condensed Matter 9, no. 27 (July 7, 1997): 5889–920. http://dx.doi.org/10.1088/0953-8984/9/27/018.

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15

Rodriguez, J. P., and Pascal Lederer. "De Haas-Van Alphen and Shubnikov-De Haas Oscillations in Strongly Correlated Electron Gas." International Journal of Modern Physics B 06, no. 05n06 (March 1992): 497–507. http://dx.doi.org/10.1142/s0217979292000281.

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We investigate the de Haas van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations in a 2D strongly correlated electron system. The normal state is described by the fluxless phase (uniform RVB) of the t−J model. In the quantum limit, we find that conventional 2D dHvA sawtooth behavior is unattainable: in the limit near half-filling, where the magnetic energy dominates, one has square wave dHvA behavior with reduced amplitude; far from half-filling one finds a mixed square wave-sawtooth regime. The dHvA oscillation frequency is unchanged in all regimes, and it corresponds to Luttinger’s Fermi surface. A conventional SdH effect exists in the above mentioned conventional regime, whereas it is absent in the square-wave dHvA regime. Lastly, it is shown that the linear-in-T contribution to the resistivity arising from chiral fluctuations in the fluxless phase dissappears in the presence of magnetic field in the quantum limit. We therefore predict that this strongly correlated metal shows a large negative magneto-resistance.
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16

Buks, E., M. Heiblum, Y. Levinson, and H. Shtrikman. "Scattering of a two-dimensional electron gas by a correlated system of ionized donors." Semiconductor Science and Technology 9, no. 11 (November 2, 1994): 2031–41. http://dx.doi.org/10.1088/0268-1242/9/11/001.

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17

Кулик, Л. В., А. В. Горбунов, А. С. Журавлев, В. Б. Тимофеев, and И. В. Кукушкин. "Двумерные триплетные магнитоэкситоны и магнетофермионный конденсат в GaAs/AlGaAs гетероструктурах." Физика твердого тела 60, no. 8 (2018): 1597. http://dx.doi.org/10.21883/ftt.2018.08.46255.01gr.

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AbstractA fundamentally new collective state, namely, the magnetofermionic condensate, is discovered during photoexcitation of a sufficiently dense gas of long-lived triplet cyclotron magnetoexcitons in a twodimensional Hall insulator with a high electron mobility, a filling factor of ν = 2, and temperatures of T < 1 K. The condensed phase coherently interacts with an external electromagnetic field, exhibits superradiant properties in the recombination of correlated condensate electrons with heavy holes in the valence band, and spreads nondissipatively in the layer of a two-dimensional electron gas to macroscopical large distances, transferring an integer spin. The observed effects are explained in terms of a coherent condensate in a nonequilibrium system of two-dimensional fermions with a fully quantized energy spectrum, in which a degenerate ensemble of long-lived triplet magnetoexcitons obeying the Bose statistics is present.
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18

Jones, R. S., and S. B. Trickey. "Correlated wavefunctions for crystalline solids. II. The metal-insulator transition in the cubic electron gas." Journal of Physics C: Solid State Physics 18, no. 34 (December 10, 1985): 6355–68. http://dx.doi.org/10.1088/0022-3719/18/34/007.

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19

Jones, R. S., and S. B. Trickey. "Correlated wavefunctions for crystalline solids: II. The metal-insulator transition in the cubic electron gas." Journal of Physics C: Solid State Physics 21, no. 18 (June 30, 1988): 3475. http://dx.doi.org/10.1088/0022-3719/21/18/512.

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20

Clikeman, Tyler T., Eric V. Bukovsky, Igor V. Kuvychko, Long K. San, Shihu H. M. Deng, Xue-Bin Wang, Yu-Sheng Chen, Steven H. Strauss, and Olga V. Boltalina. "Poly(trifluoromethyl)azulenes: structures and acceptor properties." Chem. Commun. 50, no. 47 (2014): 6263–66. http://dx.doi.org/10.1039/c4cc00510d.

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A family of highly trifluoromethylated azulenes prepared in a single-step high-temperature gas-phase reaction of azulene with CF3I exhibit outstanding electron accepting properties in the gas-phase and in solution that are linearly correlated with the number of CF3 groups.
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21

Monarkha, Yu P. "Magnetooscillations of temperature and microwave absorption in a highly correlated 2D electron gas on liquid helium." Low Temperature Physics 47, no. 4 (April 2021): 269–81. http://dx.doi.org/10.1063/10.0003737.

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22

Yim, Chi Ming, Dibyashree Chakraborti, Luke C. Rhodes, Seunghyun Khim, Andrew P. Mackenzie, and Peter Wahl. "Quasiparticle interference and quantum confinement in a correlated Rashba spin-split 2D electron liquid." Science Advances 7, no. 15 (April 2021): eabd7361. http://dx.doi.org/10.1126/sciadv.abd7361.

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Exploiting inversion symmetry breaking (ISB) in systems with strong spin-orbit coupling promises control of spin through electric fields—crucial to achieve miniaturization in spintronic devices. Delivering on this promise requires a two-dimensional electron gas with a spin precession length shorter than the spin coherence length and a large spin splitting so that spin manipulation can be achieved over length scales of nanometers. Recently, the transition metal oxide terminations of delafossite oxides were found to exhibit a large Rashba spin splitting dominated by ISB. In this limit, the Fermi surface exhibits the same spin texture as for weak ISB, but the orbital texture is completely different, raising questions about the effect on quasiparticle scattering. We demonstrate that the spin-orbital selection rules relevant for conventional Rashba system are obeyed as true spin selection rules in this correlated electron liquid and determine its spin coherence length from quasiparticle interference imaging.
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23

Schreiber, Katherine A., and Gábor A. Csáthy. "Competition of Pairing and Nematicity in the Two-Dimensional Electron Gas." Annual Review of Condensed Matter Physics 11, no. 1 (March 10, 2020): 17–35. http://dx.doi.org/10.1146/annurev-conmatphys-031119-050550.

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Due to its extremely rich phase diagram, the two-dimensional electron gas exposed to perpendicular magnetic fields has been the subject of intense and sustained study. One particularly interesting problem in this system is that of the half-filled Landau level, where the Fermi sea of composite fermions, a fractional quantum Hall state arising from a pairing instability of the composite fermions, and the quantum Hall nematic were observed in the half-filled N = 0, N = 1, and N ≥ 2 Landau levels, respectively. Thus, different ground states developed in different half-filled Landau levels. This situation has recently changed, when evidence for both the paired fractional quantum Hall state and the quantum Hall nematic was reported in the half-filled N = 1 Landau level. Furthermore, a direct quantum phase transition between these two ordered states was found. These results highlight an intimate connection between pairing and nematicity, which is a topic of current interest in several strongly correlated systems, in a well-understood and low-disorder environment.
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24

McMullen, T., P. Jena, and S. N. Khanna. "Screening of a Positive Muon by a Semion Gas." International Journal of Modern Physics B 05, no. 10 (June 1991): 1579–88. http://dx.doi.org/10.1142/s0217979291001486.

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μSR is one of the experimental techniques used to search for manifestations of the broken [Formula: see text] and [Formula: see text] symmetries predicted by some theories of highly correlated electron systems. When [Formula: see text] and [Formula: see text] are broken, the screening of the positively charged muon by the electron system generates a magnetic field in addition to any intrinsic magnetic field that may be present. We estimate the magnetic field that is induced at a muon site when the muon is screened by the fractional statistics gas. The value depends on the distance between the muon and the anyon plane, and a simple theoretical approach to the calculation of the minimum energy muon sites is outlined and some results for Bi 2 Sr 2 CaCu 2 O 8 and YBa 2 Cu 3 O 7 are presented.
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25

Tanner, Dennis D., Natasha Deonarian, and Abdelmajid Kharrat. "Electron affinities and Marcus reorganization energies. A correlation between gas phase electron affinities and solution phase redox potentials." Canadian Journal of Chemistry 67, no. 1 (January 1, 1989): 171–75. http://dx.doi.org/10.1139/v89-028.

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Redox potentials determined by cyclic voltammetry were used in conjunction with published electron affinities to determine the solvation energies for series of three classes of compounds: substituted benzoquinones, substituted nitrobenzenes, and polynuclear aromatic hydrocarbons. Excellent linear correlations were obtained between the measured electron affinities and the E0 of the substrates. The calculated electron affinities, EA (E0), were computed using the average solvation energies for the three classes of compounds, and were found to be in excellent agreement with the measured values. The nitrobenzenes and quinones had one solvation energy, while the aromatic hydrocarbons were correlated with a significantly different value. The solvation energy of a variety of compounds could also be related to their Marcus reorganization energiesλ(0), by a linear plot with a high correlation coefficient. From simple electrochemical measurements of similar compounds, either electron affinities or Marcus λ(0) values can be estimated. Keywords: electron affinities, Marcus reorganization energies, cyclic voltammetry.
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26

STROCOV, V. N., P. O. NILSSON, R. CLAESSEN, F. ARYASETIAWAN, P. BLAHA, J. M. THEMLIN, G. NICOLAY, and S. HÜFNER. "SELF-ENERGY EFFECTS IN THE UNOCCUPIED AND OCCUPIED ELECTRONIC STRUCTURE OF Cu." Surface Review and Letters 09, no. 02 (April 2002): 1281–85. http://dx.doi.org/10.1142/s0218625x02003706.

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We report on self-energy effects in the electronic structure of Cu as a prototype weakly correlated system containing electron states of different localization. The unoccupied and occupied excited states were mapped fully resolved in the three-dimensional k using very-low-energy electron diffraction and photoemission, respectively. The self-energy corrections to the density-functional theory show distinct band- and k-dependence. These results are well described by quasiparticle GW calculations, especially for less localized states. We find correlation of the self-energy effects with spatial overlap of the one-electron wave function with the electron density, and elucidate the essential physics of this effect based on the electron-gas exchange correlation behavior.
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27

Ghirardini, V., S. Ettori, D. Eckert, and S. Molendi. "Polytropic state of the intracluster medium in the X-COP cluster sample." Astronomy & Astrophysics 627 (June 25, 2019): A19. http://dx.doi.org/10.1051/0004-6361/201834875.

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Aims. In this work, we have investigated the relation between the radially resolved thermodynamic quantities of the intracluster medium in the X-COP cluster sample, aiming to assess the stratification properties of the ICM. Methods. We modeled the relations between radius, gas temperature, density, and pressure using a combination of power-laws, also evaluating the intrinsic scatter in these relations. Results. We show that the gas pressure is remarkably well correlated to the density, with very small scatter. Also the temperature correlates with gas density with similar scatter. The slopes of these relations have values that show a clear transition from the inner cluster regions to the outskirts. This transition occurs at the radius rt = 0.19(±0.04) R500 and electron density nt = (1.91 ± 0.21) × 10−3 cm−3 E2(z). We find that above 0.2 R500 the radial thermodynamic profiles are accurately reproduced by a well defined and physically motivated framework, where the dark matter follows the NFW potential and the gas is represented by a polytropic equation of state. By modeling the gas temperature dependence upon both the gas density and radius, we propose a new method to reconstruct the hydrostatic mass profile based only on the relatively inexpensive measurement of the gas density profile.
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28

NAJAFI, MEYSAM, MOHAMMAD NAJAFI, and HOUSHANG NAJAFI. "THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER." Journal of Theoretical and Computational Chemistry 12, no. 02 (March 2013): 1250116. http://dx.doi.org/10.1142/s0219633612501167.

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In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET–PT, and SPLET, for mono-substituted Stobadines were calculated in gas-phase and water. Results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with the indolic N–H bond length after electron abstraction, R(N–H+•), and the partial charge on the indolyl radical nitrogen atom, q( N ). Furthermore, calculated IP and PA values for mono-substituted Stobadines show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ) of studied molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in water.
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29

Roy, Chinmay, Aparna Ghosh, and Suman Chatterjee. "Role of defects in electron band structure and gas sensor response of La2CuO4." Sensor Review 40, no. 6 (November 4, 2020): 675–85. http://dx.doi.org/10.1108/sr-12-2019-0319.

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Purpose This paper aims to estimate the relationship between defect structure with gas concentration for use as a gas sensor. The change in defect concentration caused a shift in the Fermi level, which in turn changed the surface potential, which is manifested as the potentiometric response of the sensing element. Design/methodology/approach A new theoretical concept based on defect chemistry and band structure was used to explain the experimental gas response of a sensor. The theoretically simulated response was compared with experimental results. Findings Understanding the origin of potentiometric response, through the generation of defects and a corresponding shift in Fermi level of sensing surface, by the adsorption of gas. Through this understanding, the design of a sensor with improved selectivity and stability to a gas can be achieved by the study of defect structure and subsequent band analysis. Research limitations/implications This paper provides information about various types of surface defects and numerical simulation of material with defect structure. The Fermi energy of the simulated value is correlated with the potentiometric sensor response. Practical implications Gas sensors are an integral part of vehicular and industrial pollution control. The theory developed shows the origin of response which can help in identifying the best sensing material and its optimum temperature of operation. Social implications Low-cost, reliable and highly sensitive gas sensors are highly demanded which is fulfilled by potentiometric sensors. Originality/value The operating principle of potentiometric sensors is analyzed through electron band structure analysis. With the change in measured gas concentration, the oxygen partial pressure changes. This results in a change in defect concentration in the sensing surface. Band structure analysis shows that change in defect concentration is associated with a shift in Fermi level. This is the origin of the potentiometric response.
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30

Cliffe, Matthew, Wei Wan, Xiaodong Zou, François-Xavier Coudert, and Andrew Goodwin. "Correlated defects in group 4 metal-organic frameworks." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1124. http://dx.doi.org/10.1107/s2053273314088755.

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The importance of defects for inorganic functional framework materials is well established, being crucial for properties from relaxor ferroelectricity to superconductivity. The corresponding study of defects in metal-organic frameworks (MOFs) is still however in its infancy. Recent studies have established that ligand-absence defects can be controllably introduced into frameworks and that these defects can drastically improve the material properties, but have so far shown no evidence of correlation between defects. Much of this research has focussed on UiO-66, a zirconium dicarboxylate MOF that was amongst the first very stable MOFs to be discovered.[1] As a result of its stability, it and its derivatives have been investigated for a wide range of properties including photo- and Brønsted acid catalysis, sensing and gas sorption properties. The ability to introduce defects has been demonstrated to substantially enhance both the sorption and catalytic properties of UiO-66.[2][3] We have demonstrated, using a combination of powder X-ray diffraction, total scattering and electron diffraction measurements, that UiO-66 can be engineered, under the appropriate synthetic conditions, to accommodate correlated defect nanodomains. These correlations offer exciting opportunities for manipulating the physical properties, including mass transport, chemical activity and mechanical flexibility.
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31

Najafi, Meysam, Mohammad Najafi, and Houshang Najafi. "DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Sesamol Derivatives in the Gas phase and water." Canadian Journal of Chemistry 90, no. 10 (October 2012): 915–26. http://dx.doi.org/10.1139/v2012-087.

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In this paper, the study of various ortho and meta–substituted Sesamol derivatives is presented. The reaction enthalpies related to three antioxidant action mechanisms HAT, SET–PT, and SPLET for substituted Sesamols, have been calculated using the DFT/B3LYP method in gas phase and water. Calculated results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In the ortho position, substituents show a larger effect on reaction enthalpies than in the meta position. In comparison with the gas phase, water attenuates the substituent effect on all reaction enthalpies. In the gas phase, BDEs are lower than PAs and IPs, i.e., HAT represents the thermodynamically preferred pathway. On the other hand, the SPLET mechanism represents the thermodynamically favored process in water. Results show that calculated enthalpies can be successfully correlated with Hammett constants (σm) of the substituted Sesamols. Furthermore, calculated IP and PA values for substituted Sesamols show linear dependence on the energy of the highest occupied molecular orbital (EHOMO).
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32

Abdul Hamid, Haslinda, and M. N. Abdul Hadi. "The Study of Al-N Codoped ZnO Thin Films Prepared by DC Magnetron Sputtering." Applied Mechanics and Materials 754-755 (April 2015): 591–94. http://dx.doi.org/10.4028/www.scientific.net/amm.754-755.591.

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The codoped ZnO thin film were deposited by DC magnetron sputtering on silicon (111) followed by annealing treatment at 200 °C and 600 °C for 1 hour in nitrogen and oxygen gas mixture. Structural investigation was carried out by scanning electron microscopy (SEM), atomic force microscopy and x-ray diffraction (XRD). Film roughness and grain shape were found to be correlated with the annealing temperatures.
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33

Ma, Yuanzhen, Meng Wang, Ruying Ma, Jiamin Li, Asiya Bake, and Yadi Shan. "Micropore Characteristics and Gas-Bearing Characteristics of Marine-Continental Transitional Shale Reservoirs in the East Margin of Ordos Basin." Adsorption Science & Technology 2021 (May 22, 2021): 1–15. http://dx.doi.org/10.1155/2021/5593245.

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In order to deeply study the exploration potential of Carboniferous-Permian marine-continental transitional shale reservoirs in the Ordos Basin, the shale samples from well Y1 in the central-southern part of the Hedong Coalfield were used as the research object. The organic geochemical test, scanning electron microscope, X-ray diffraction, and high pressure mercury injection and low-temperature nitrogen adsorption experiments have studied the microscopic characteristics and gas content characteristics of shale reservoirs. The results show that the organic matter type of the sample is type III; the TOC content ranges from 0.28% to 16.87%, with an average of 2.15%; R o is from 2.45% to 3.36%, with an average value of 2.86%; the shale pores in the study area are well developed, containing more organic pores and intergranular pores of clay minerals. Based on the two-dimensional SEM image fractal theory to study different types of pores, the fractal dimension of shale pore fracture morphology is between 2.34 and 2.50, and the heterogeneity is moderate. The high-pressure mercury intrusion experiment characterizes the pore size distribution of shale macropores and transition pores. The pore diameters are mostly nm-scale. Transition pores are the main pores of the shale in the study area. Based on the characteristics of the pore structure, the adsorption capacity and gas content of CH4 in shale reservoir were analyzed by methane isothermal adsorption and gas content experiments. The results showed that the pore volume and specific surface area were positively correlated with clay mineral content, TOC, and RO, but negatively correlated with the quartz content. In clay minerals and brittle minerals, pore volume and specific surface area are positively correlated with illite content and negatively correlated with the quartz and kaolinite content. The measured total gas content and desorbed gas content are significantly positively correlated with TOC, but are weakly positively correlated with the quartz and illite content. This study finely characterizes the physical properties, micropore characteristics, gas-bearing characteristics, and influencing factors of shale reservoirs, which has certain theoretical guiding significance for the research and development of coal-measure shale in the Ordos Basin.
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34

Gyani, Angeli K., Phillip McClusky, David S. Urch, M. Charbonnicr, F. Gaillard, and M. Romand. "Non-Destructive Chemical-State Analysis of Thin Films and Surface Layers (1-1000 nm) by Low-Energy Electron-Induced X-ray Spectroscopy (LEEIXS)." Advances in X-ray Analysis 33 (1989): 247–59. http://dx.doi.org/10.1154/s0376030800019649.

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AbstractThe penetration depth of 1-12 keV electrons in most materials is less than one micron and the characteristic soft x-rays that are produced can be used to identify the elements present in the surface. Varying the energy of the incident electron beam enables the depth of analysis to be controlled.Soft x-rays often exhibit large 'chemical effects' (changes in peak profile and peak position) which can he correlated with chemical changes. A study of such effects for each element present in the sample surface, as a function of electron-beam energy, can in some cases, permit changes in the chemical state (valency - coordination number-spin state etc.) to be determined as a function of depth.Such analyses can be carried out either in a conventional x-ray spectrometer in which the x-ray tube has been replaced by a gas-discharge source, or in a spectrometer in which the sample is bombarded with electrons from a normal electron gun. In this paper these techniques are outlined and some applications reviewed:- the analysis of oxide layers on aluminium and steel, the analysis of aluminium-nitride layers produced by MOCVD on gallium arsenide, the analysis of silica fiims (with added boron and phosphorus oxides) on silicon and the analysis of zinc-oxide films on glass.
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35

Tsai, Cheng-Cheng, Yu-Wei Lu, and Wei-Ping Hu. "Theoretical Prediction on the New Types of Noble Gas Containing Anions OBONgO− and OCNNgO− (Ng=He, Ar, Kr and Xe)." Molecules 25, no. 24 (December 10, 2020): 5839. http://dx.doi.org/10.3390/molecules25245839.

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The fluorine-less noble gas containing anions OBONgO− and OCNNgO− have been studied by correlated electronic structure calculation and density functional theory. The obtained energetics indicates that for Ng=Kr and Xe, these anions should be kinetically stable at low temperature. The molecular structures and electron density distribution suggests that these anions are stabilized by ion-induced dipole interactions with charges concentrated on the electronegative OBO and OCN groups. The current study shows that in addition to the fluoride ion, polyatomic groups with strong electronic affinities can also form stable noble gas containing anions of the type Y−…NgO.
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36

Hadisaputra, Saprizal, Harno Dwi Pranowo, and Ria Armunanto. "EXTRACTION OF STRONTIUM(II) BY CROWN ETHER: INSIGHTS FROM DENSITY FUNCTIONAL CALCULATION." Indonesian Journal of Chemistry 12, no. 3 (December 28, 2012): 207–16. http://dx.doi.org/10.22146/ijc.21332.

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The structures, energetic and thermodynamic parameters of crown ethers with different cavity size, electron donating/withdrawing substituent groups and donor atoms have been determined with density functional method at B3LYP level of theory in gas and solvent phase. Small core quasi-relativistic effective core potentials was used together with the accompanying SDD basis set for Sr2+ and DZP basis set was used for crown ether atoms. Natural bond orbital (NBO) analysis was evaluated to characterize the distribution of electrons on the complexes. The interaction energy is well correlated with the values of Strontium charge after complexation, the second order interaction energies (E2) and HOMO-LUMO energy gab (∆Egab). The interaction energy and thermodynamics parameters in gas phase are reduced in solvent phase as the solvent molecules weaken the metal-crown ether interaction. The thermodynamic parameters indicated that less feasibility to extract Sr2+ ion directly from pure water without presence of organic solvent. The theoretical values of extraction energy for Sr(NO3)2 salt from aqueous solution in different organic solvent is validated by the experimental trend. This study would have strong contribution in planning the experiments to the design of specific host ligand and screening of solvent for extraction of metal ion.
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37

Wei, Xiaoliang, Qian Chen, Jinchuan Zhang, Haikuan Nie, Wei Dang, Zhongming Li, Xuan Tang, Yue Lang, and Lamei Lin. "Nanoscale Pore Fractal Characteristics of Permian Shale and Its Impact on Methane-Bearing Capacity: A Case Study from Southern North China Basin, Central China." Journal of Nanoscience and Nanotechnology 21, no. 1 (January 1, 2021): 139–55. http://dx.doi.org/10.1166/jnn.2021.18462.

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Fractal dimension is closely related to the nanoscale pore structure of shale, and it also has an important influence on the gas content of shale. To investigate the correlation between the fractal dimension and the methane (CH4) bearing features of shale, seven Permian shale samples were analyzed with field emission scanning electron microscopy (FE-SEM), low temperature nitrogen (N2), carbon dioxide (CO2) and CH4 adsorption and on-site gas desorption experiments. Based on the N2 adsorption and desorption data, we proposed a new method to better determine the gas adsorption stage at different relative pressure (P/P0) points in the multilayer adsorption or capillary condensation stage. On this basis, two fractal dimensions, D1 (representing the surface roughness) and D2 (representing pore irregularity), were obtained. By correlating the fractal dimensions and nanoscale pore structure parameters, we found that D1 does not correlate with the pore structure parameters except for the micropore volume. Influenced by the aggregation of porous and nonporous materials, D2 has a positive linear relationship with the specific surface area (SSA) and micropore volume but has a negative linear correlation with the average diameter of pores. D1 is negatively correlated with water saturation and positively correlated with free CH4 content. The CH4 adsorption content is positively correlated with D2. By fitting the on-site desorption data, the positive correlation between the total desorbed CH4 content and the desorbed CH4 content in stage 2 and D2 was also confirmed. D2 better reflects the CH4 adsorption capacity of organic-rich shale than D1. However, D1 can be used to reflect the influence of shale surface properties on water saturation and to indirectly reflect the free CH4 content in shale. The fractal dimension (D1 and D2) is a clear indicator of the total free and adsorbed CH4 content, but cannot indicate the desorbed CH4 content at different stages.
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38

Elafandi, Salah, Zabihollah Ahmadi, Nurul Azam, and Masoud Mahjouri-Samani. "Gas-Phase Formation of Highly Luminescent 2D GaSe Nanoparticle Ensembles in a Nonequilibrium Laser Ablation Process." Nanomaterials 10, no. 5 (May 8, 2020): 908. http://dx.doi.org/10.3390/nano10050908.

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Interest in layered two-dimensional (2D) materials has been escalating rapidly over the past few decades due to their promising optoelectronic and photonic properties emerging from their atomically thin 2D structural confinements. When these 2D materials are further confined in lateral dimensions toward zero-dimensional (0D) structures, 2D nanoparticles and quantum dots with new properties can be formed. Here, we report a nonequilibrium gas-phase synthesis method for the stoichiometric formation of gallium selenide (GaSe) nanoparticles ensembles that can potentially serve as quantum dots. We show that the laser ablation of a target in an argon background gas condenses the laser-generated plume, resulting in the formation of metastable nanoparticles in the gas phase. The deposition of these nanoparticles onto the substrate results in the formation of nanoparticle ensembles, which are then post-processed to crystallize or sinter the nanoparticles. The effects of background gas pressures, in addition to crystallization/sintering temperatures, are systematically studied. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, and time-correlated single-photon counting (TCSPC) measurements are used to study the correlations between growth parameters, morphology, and optical properties of the fabricated 2D nanoparticle ensembles.
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39

Nakahara, Sumio, S. C. Langford, and J. T. Dickinson. "Chemisorptive electron emission and atomic force microscopy as probes of plastic deformation during fracture at a metal/glass interface." Journal of Materials Research 10, no. 8 (August 1995): 2033–41. http://dx.doi.org/10.1557/jmr.1995.2033.

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We examine the use of chemisorptive emission (electron emission accompanying the adsorption of a reactive gas on a metal surface) and atomic force microscopy as measures of plastic deformation during fracture along a metallic Mg/glass interface. Localized ductile deformation in the metallic phase enhances the fracture energy, exposes metallic Mg to the reactive O2 atmosphere, and produces intense emissions. The number of electrons emitted following fracture in low-pressure oxygen atmospheres is strongly correlated with the total energy expended during failure (peel energy). The presence of localized ductile deformation is verified by atomic force microscopy (AFM): voids are observed on surfaces yielding significant cmissions and enhanced fracture energies. These voids are not observed on samples yielding the lowest peel energies and emission intensities, i.e., where the contribution of deformation to the peel energy is negligible. Quantitative use of roughness data derived from the AFM images is, however, problematic. The potential for chemisorptive electron emission as a probe of deformation along interfaces involving Mg, Ti, Zr, and Al is promising.
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40

Tehniat, Saba, Shazia Bashir, Khaliq Mahmood, and Ayesha Sharif. "Surface morphology correlated with sputtering yield measurements of laser-ablated iron." Laser and Particle Beams 36, no. 3 (September 2018): 427–41. http://dx.doi.org/10.1017/s0263034618000435.

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AbstractIron (Fe) targets are exposed to 100 pulses of Nd: YAG laser (532 nm, 6 ns, 10 Hz) at various fluences ranging from 4.8 to 38.5 J/cm2. In order to explore the effect of background environment, targets have been exposed under vacuum as well as under five different pressures ranging from 5 to 100 Torr of various background gases like Ar, Ne, O2, and air. The sputtering yield measurements and surface modifications of laser-ablated Fe are explored by quartz crystal microbalance (QCM) and scanning electron microscopy (SEM) analysis, respectively. QCM measurements reveal that the sputtering yield of Fe is strongly affected by laser fluence, pressure and nature of gas. By increasing laser fluence, the sputtering yield initially increases due to enhanced energy deposition and then saturates due to self-regulating regime. However, with increasing pressures of background gases, the sputtering yield of Fe initially increases and then decreases. Owing to thermal conductivity, ionization potential, and mass of background gas, the sputtering yield of Fe varies in accordance with the sequence vacuum >Ar>Ne>O2> air. The SEM analysis reveals the formation of several features like laser-induced periodic surface structures, cones, cavities, channels, multiple ablative craters, and dot-like structures. The difference in the periodicity, size, and shape of features is explained on the basis of confinement and shielding effects of plasma and various energy deposition mechanisms. The surface profilometry analysis reveals that the crater depth increases with increasing the laser fluence in inert environments, while in case of reactive environments, it tends to decrease initially and afterwards it increases. X-ray diffraction and energy-dispersive X-ray analyses confirm the oxide formation in case of Fe treatment in O2 and air; however, no additional phases are observed for Fe irradiation under inert environments.
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41

Hamid, Haslinda Abdul, Hooi Min Yee, and Mohd Nasir Abdul Hadi. "The Fabrication of Codoped ZnO Thin Films by DC Magnetron Sputtering." Key Engineering Materials 594-595 (December 2013): 958–61. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.958.

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The codoped ZnO thin film were deposited by DC magnetron sputtering on silicon (111) followed by annealing treatment at 400 °C and 600 °C for 1 hour in nitrogen and oxygen gas mixture. Structural investigation was carried out by scanning electron microscopy (SEM) and X ray diffraction (XRD). Film roughness (r.m.s) and grain shape were found to be correlated with the annealing temperatures. SEM result has shown that its surface characteristics are strongly influenced by annealing temperatures.
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42

Wu, Hao, Youliang Ji, Ruie Liu, Chunlin Zhang, and Sheng Chen. "Pore structure and fractal characteristics of a tight gas sandstone: A case study of Sulige area in the Ordos Basin, China." Energy Exploration & Exploitation 36, no. 6 (March 22, 2018): 1438–60. http://dx.doi.org/10.1177/0144598718764750.

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To understand the pore structure and fractal characteristics of tight gas reservoirs, thin sections, nuclear magnetic resonance, rate-controlled mercury injection, microcomputed tomography scanning, and field emission scanning electron microscopy investigations under laboratory conditions were conducted on a suite of core samples from the Middle Permian Shihezi Formation of Sulige area in the Ordos Basin, China. The investigated tight gas sandstones comprise three types of pores, i.e. residual intergranular pore, secondary dissolution pore, and micropore. The pore–throat size distribution is extremely wide and multiscale (10 nm–400 μm) co-existing in tight gas reservoirs. The submicron- and micron-scale pore–throats with radius above 0.05 μm, which are characterized by combining rate-controlled mercury injection with nuclear magnetic resonance, are considered to be the effective pores and throats that dominated the reservoirs flow capacity. Tight gas sandstones have stage fractal characteristics, and the intrusion pressure of approximately 1 MPa is regarded as an inflection point. Fractal dimension is negatively correlated with permeability, average throat radius and mainstream throat radius, positively correlated with heterogeneous coefficient, while there are no obvious relationships with porosity and average pore radius. Additionally, the percolation characteristics of tight gas reservoirs can be characterized by fractal structure. When the pore structure does not follow the fractal structure (i.e. intrusion pressure is lower than 1 MPa), the mercury intrusion saturation is dominated by pores; in contrast, the mercury intrusion saturation is almost solely dominated by throats. This research sheds light on the pore–throat size distribution of tight gas reservoirs by identifying the role of multiple techniques and the relationships between the pore structure parameters and percolation characteristics of tight gas reservoirs and fractal dimension.
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43

Sugiyama, Haruki, and Hidehiro Uekusa. "Two-step crystal–crystal phase transformation of N-salicylidene-p-aminobenzoic acid by gas–solid reaction with aqua–ammonia vapour." Acta Crystallographica Section C Structural Chemistry 77, no. 1 (January 1, 2021): 56–60. http://dx.doi.org/10.1107/s2053229620016411.

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Crystal–crystal phase transformation by external stimuli has attracted significant attention for application in switchable materials, which can change their structures and properties. Herein, it is revealed that N-salicylidene-p-aminobenzoic acid crystals undergo a two-step crystal–crystal phase transformation through a gas–solid reaction with aqua–ammonia vapour. The photochromic behaviour of the crystals switched from nonphotochromic to photochromic and back to nonphotochromic via a phase transformation. The two-step phase transformation and photochromic behaviour change were characterized and correlated by X-ray crystal structure analysis, UV–Vis spectroscopy, differential scanning calorimetry and scanning electron microscopy. This article is the first report to capture the stepwise structural change in the gas–solid (acid–base) reaction of ammonia with benzoic acid derivatives.
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44

Moustakidis, Ch C., and S. E. Massen. "Dependence of Information Entropy of Uniform Fermi Systems on Correlations and Thermal Effects." HNPS Proceedings 13 (February 20, 2020): 173. http://dx.doi.org/10.12681/hnps.2968.

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The influence of correlations of uniform Fermi systems (nuclear matter, electron gas and liquid 3He) on Shannon's information entropy, S, is studied. It is found that, for three different Fermi systems with different particle interactions, the correlated part of S (Soor) depends on the correlation parameter of the systems or on the discontinuity gap of the momentum distribution through two parameter expressions. The values of the parameters characterize the strength of the correlations. A two parameter expression also holds between Scor and the mean kinetic energy (K) of the Fermi system. The study of thermal effects on the uncorrelated electron gas leads to a relation between the thermal part of S (Sthermai) and the fundamental quantities of temperature, thermodynamical entropy and the mean kinetic energy. It is found that, in the case of low temperature limit, the expression connecting Sthermai with Κ is the same to the one which connects Scor with K. Thus, regardless of the reason (correlations or thermal) that changes K, S takes almost the same value.
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45

Sungthong, A., P. Khomdet, S. Porntheeraphat, C. Hruanun, Amporn Poyai, and J. Nukeaw. "Chemical Characterization and Electrical Properties of Indium Oxynitride Grown by Reactive Gas-Timing RF Magnetron Sputtering." Advanced Materials Research 93-94 (January 2010): 443–46. http://dx.doi.org/10.4028/www.scientific.net/amr.93-94.443.

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This work investigates changes in the chemical composition of InON thin films, grown by reactive gas-timing rf magnetron sputtering with different O2:N2 timing ratio characterized by Auger Electron Microscope (AES), Raman Spectroscopy which are well correlated with the electrical properties of films. The existence of nitrogen and oxygen in the deposited InON thin films was revealed by AES. Two Raman active optical phonons have been clearly observed and assigned to InN E1(TO) at ~470 cm-1 and E1(LO) at ~570 cm-1 and also shifted with different O2:N2 timing ratio. The carrier mobility of InON thin films was decreased when the ratio of O2:N2 timing is increased.
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46

Spies, Lothar, Walter Apel, and Bernhard Kramer. "Exact density of states of a two-dimensional electron gas in a strong magnetic field and a long-range correlated random potential." Physical Review B 55, no. 7 (February 15, 1997): 4057–60. http://dx.doi.org/10.1103/physrevb.55.4057.

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47

Qiao, Peng, Yiwen Ju, Jianchao Cai, Jun Zhao, Hongjian Zhu, Kun Yu, Yu Qi, et al. "Micro-Nanopore Structure and Fractal Characteristics of Tight Sandstone Gas Reservoirs in the Eastern Ordos Basin, China." Journal of Nanoscience and Nanotechnology 21, no. 1 (January 1, 2021): 234–45. http://dx.doi.org/10.1166/jnn.2021.18743.

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The complex pore system in tight sandstone reservoirs controls the storage and transport of natural gas. Thus, quantitatively characterizing the micro-nanopore structure of tight sandstone reservoirs is of great significance to determining the accumulation and distribution of tight gas. The pore structure of reservoirs was determined through polarizing microscopy, scanning electron microscopy (SEM), and the combination of mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) experiments on Late Paleozoic conventional and tight sandstone samples from the Linxing Block, Ordos Basin. The results show that in contrast to conventional sandstone, dissolution pores, with diameters less than 8 μm, are the main contributors to the gas storage space of tight sandstone reservoirs. The pore size distribution derived from the MICP experiment demonstrates that the main peak of tight sandstones corresponds to a pore radius in the range of 247 nm to 371 nm, while the secondary peak usually corresponds to 18 nm. The results of the NMR test illustrate that the T2 spectra of tight sandstones are unimodal, bimodal and multimodal, and the main NMR peak is highly related to the MICP peak. Fractal theory was proposed to quantitatively characterize the complex pore structure and rough porous surface. The sandstones show fractal characteristics including nanopore fractal dimension DN obtained from the MICP and large pore fractal dimension DL obtained from the NMR experiment. Both DN and DL are positively correlated with porosity and negatively correlated with permeability, demonstrating that complex and heterogeneous pore structure could increase the gas storage space and reduce the connectivity.
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48

M., Vinoth Kumar, and Balasubramanian V. "Effect of current pulsing on super 304HCu weld joints." World Journal of Engineering 16, no. 6 (December 2, 2019): 814–22. http://dx.doi.org/10.1108/wje-07-2019-0207.

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Purpose Super 304HCu super austenitic stainless steel tubes containing 2.3 to 3 (Wt.%) of copper (Cu) is used in superheaters and reheater tubings of nuclear power plants. In general, austenitic stainless steels welded by conventional constant current gas tungsten arc welding (CC-GTAW) produce coarse columnar grains, alloy segregation and may result in inferior mechanical properties. Pulsed current gas tungsten arc welding (PC-GTAW) can control the solidification structure by altering the prevailing thermal gradients in the weld pool. Design/methodology/approach Super 304HCu tubes of Ø 57.1 mm and the wall thickness of 3.5 mm were autogenously welded using CC and PC-GTAW processes. Joints are characterized using optical microscopy, electron microscopy, energy dispersive spectroscopy and electron backscatter diffraction (EBSD) techniques. Hot tensile properties of the weld joints were evaluated and correlated with their microstructural features. Findings Current pulsing in GTAW has resulted in minimal eutectic film segregation, lower volume % of delta ferrite and appreciable improvement in tensile properties than CC-GTAW joints. Originality/value The EBSD boundary map and inverse pole orientation map of Super 304HCu weld joints evidence the grain refinement and much frequent high angle grain boundaries achieved using weld current pulsing.
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49

Gianoglio, Dario, Nevaf Ciftci, Sarah Armstrong, Volker Uhlenwinkel, and Livio Battezzati. "On the Cooling Rate-Microstructure Relationship in Molten Metal Gas Atomization." Metallurgical and Materials Transactions A 52, no. 9 (June 23, 2021): 3750–58. http://dx.doi.org/10.1007/s11661-021-06325-2.

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AbstractGas atomization is the most used powder production technique since it provides good control on particles shape, surface oxidation and dimension. It is a rapid solidification technique involving fast cooling rates, which are strictly correlated to particle size. This relationship is typically described with a power law function that can be determined experimentally by measuring the microstructural length-scale or through the application of a heat transfer model. Both paths were exploited in the present work focusing on a gas-atomized Al-4.5Cu alloy. Atomized powders were characterized by means of X-ray diffraction, differential scanning calorimetry, light and scanning electron microscopy to investigate the relationship between cooling rate and microstructure length-scale. A recently proposed semi-empirical model was validated and discussed in terms of a physically based heat transfer approach. The change in gas-to-melt mass flow ratio (GMR) was also investigated showing that it does not affect appreciably the relationship between solidification rate and particle size, but does increase the Cu supersaturation in the powders of finer size.
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50

Hadisaputra, Saprizal, Saprini Hamdiani, Muhammad Arsyik Kurniawan, and Nuryono Nuryono. "Influence of Macrocyclic Ring Size on the Corrosion Inhibition Efficiency of Dibenzo Crown Ether: A Density Functional Study." Indonesian Journal of Chemistry 17, no. 3 (November 30, 2017): 431. http://dx.doi.org/10.22146/ijc.26667.

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The effect of macrocycle ring size on the corrosion inhibition efficiency of dibenzo-12-crown-4 (DB12C4), dibenzo-15-crown-5 (DB15C5), dibenzo-18-crown-6 (DB18C6), dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) have been elucidated by mean of density functional calculation at B3LYP/6-31G(d) level of theory in the gas and aqueous environment. The quantum chemical parameters including the frontier orbital energies (EHOMO, ELUMO), ionization potential (I), electron affinity (A), the absolute electronegativity (χ), hardness (η), softness (σ), and the fraction of electron transferred (ΔN) are positively correlated to the corrosion inhibition efficiency (IE%) of the studied crown ethers. The calculation results indicate that DB24C8 exhibits the highest corrosion inhibition efficiency, whereas DB12C4 exhibits the lowest corrosion inhibition efficiency. The results of this study will contribute to design crown ethers potential as corrosion inhibitors.
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