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Letteratura scientifica selezionata sul tema "Hirshfeld Atom Refinement"

Autore: Grafiati

Pubblicato: 8 giugno 2024

Ultima modifica: 31 luglio 2025

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Articoli di riviste sul tema "Hirshfeld Atom Refinement"

Grabowsky, Simon, Magdalena Woinska, and Dylan Jayatilaka. "Hirshfeld Atom Refinement." Nihon Kessho Gakkaishi 58, Supplement (2016): s18. http://dx.doi.org/10.5940/jcrsj.58.s18.

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Capelli, Silvia C., Hans-Beat Bürgi, Birger Dittrich, Simon Grabowsky, and Dylan Jayatilaka. "Hirshfeld atom refinement." IUCrJ 1, no. 5 (2014): 361–79. http://dx.doi.org/10.1107/s2052252514014845.

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Abstract (sommario):

Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-madeab initioquantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustratedviathe example of c

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Midgley, Laura, Luc J. Bourhis, Oleg V. Dolomanov, et al. "Vanishing of the atomic form factor derivatives in non-spherical structural refinement – a key approximation scrutinized in the case of Hirshfeld atom refinement." Acta Crystallographica Section A Foundations and Advances 77, no. 6 (2021): 519–33. http://dx.doi.org/10.1107/s2053273321009086.

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Abstract (sommario):

When calculating derivatives of structure factors, there is one particular term (the derivatives of the atomic form factors) that will always be zero in the case of tabulated spherical atomic form factors. What happens if the form factors are non-spherical? The assumption that this particular term is very close to zero is generally made in non-spherical refinements (for example, implementations of Hirshfeld atom refinement or transferable aspherical atom models), unless the form factors are refinable parameters (for example multipole modelling). To evaluate this general approximation for one s

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Chodkiewicz, Michał Leszek, Magdalena Woińska, and Krzysztof Woźniak. "Hirshfeld atom like refinement with alternative electron density partitions." IUCrJ 7, no. 6 (2020): 1199–215. http://dx.doi.org/10.1107/s2052252520013603.

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Hirshfeld atom refinement is one of the most successful methods for the accurate determination of structural parameters for hydrogen atoms from X-ray diffraction data. This work introduces a generalization of the method [generalized atom refinement (GAR)], consisting of the application of various methods of partitioning electron density into atomic contributions. These were tested on three organic structures using the following partitions: Hirshfeld, iterative Hirshfeld, iterative stockholder, minimal basis iterative stockholder and Becke. The effects of partition choice were also compared wit

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Orben, Claudia M., та Birger Dittrich. "Hydrogen ADPs with CuKα data? Invariom and Hirshfeld atom modelling of fluconazole". Acta Crystallographica Section C Structural Chemistry 70, № 6 (2014): 580–83. http://dx.doi.org/10.1107/s2053229614010195.

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For the structure of fluconazole [systematic name: 2-(2,4-difluorophenyl)-1,3-bis(1H-1,2,4-triazol-1-yl)propan-2-ol] monohydrate, C13H12F2N6O·H2O, a case study on different model refinements is reported, based on single-crystal X-ray diffraction data measured at 100 K with CuKα radiation to a resolution of sin θ/λ of 0.6 Å−1. The structure, anisotropic displacement parameters (ADPs) and figures of merit from the independent atom model are compared to `invariom' and `Hirshfeld atom' refinements. Changing from a spherical to an aspherical atom model lowers the figures of merit and improves both

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Malaspina, Lorraine A., Anna A. Hoser, Alison J. Edwards, et al. "Hydrogen atoms in bridging positions from quantum crystallographic refinements: influence of hydrogen atom displacement parameters on geometry and electron density." CrystEngComm 22, no. 28 (2020): 4778–89. http://dx.doi.org/10.1039/d0ce00378f.

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Chodkiewicz, Michał, Sylwia Pawlędzio, Magdalena Woińska, and Krzysztof Woźniak. "Fragmentation and transferability in Hirshfeld atom refinement." IUCrJ 9, no. 2 (2022): 298–315. http://dx.doi.org/10.1107/s2052252522000690.

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Abstract (sommario):

Hirshfeld atom refinement (HAR) is one of the most effective methods for obtaining accurate structural parameters for hydrogen atoms from X-ray diffraction data. Unfortunately, it is also relatively computationally expensive, especially for larger molecules due to wavefunction calculations. Here, a fragmentation approach has been tested as a remedy for this problem. It gives an order of magnitude improvement in computation time for larger organic systems and is a few times faster for metal–organic systems at the cost of only minor differences in the calculated structural parameters when compar

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Woińska, Magdalena, Dylan Jayatilaka, Mark A. Spackman, et al. "Hirshfeld atom refinement for modelling strong hydrogen bonds." Acta Crystallographica Section A Foundations and Advances 70, no. 5 (2014): 483–98. http://dx.doi.org/10.1107/s2053273314012443.

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Abstract (sommario):

High-resolution low-temperature synchrotron X-ray diffraction data of the salt L-phenylalaninium hydrogen maleate are used to test the new automated iterative Hirshfeld atom refinement (HAR) procedure for the modelling of strong hydrogen bonds. The HAR models used present the first examples ofZ′ > 1 treatments in the framework of wavefunction-based refinement methods. L-Phenylalaninium hydrogen maleate exhibits several hydrogen bonds in its crystal structure, of which the shortest and the most challenging to model is the O—H...O intramolecular hydrogen bond present in the hydrogen maleate a

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Ruth, Paul Niklas, Regine Herbst-Irmer, and Dietmar Stalke. "Hirshfeld atom refinement based on projector augmented wave densities with periodic boundary conditions." IUCrJ 9, no. 2 (2022): 286–97. http://dx.doi.org/10.1107/s2052252522001385.

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Abstract (sommario):

Hirshfeld atom refinement (HAR) is an X-ray diffraction refinement method that, in numerous publications, has been shown to give H-atom bond lengths in close agreement with neutron diffraction derived values. Presented here is a first evaluation of an approach using densities derived from projector augmented wave (PAW) densities with three-dimensional periodic boundary conditions for HAR. The results show an improvement over refinements that neglect the crystal environment or treat it classically, while being on a par with non-periodic approximations for treating the solid-state environment qu

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SATO, Hiroyasu, and Akihito YAMANO. "An Overview and Examples for Hirshfeld Atom Refinement." Nihon Kessho Gakkaishi 61, no. 2 (2019): 130–35. http://dx.doi.org/10.5940/jcrsj.61.130.

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Più fonti

Tesi sul tema "Hirshfeld Atom Refinement"

Wieduwilt, Erna K. "Quantum mechanics-based methods for the refinement of crystal structures and the analysis of non-covalent interactions." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0167.

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Dans cette thèse, les orbitales moléculaires extrêmement localisées (ELMOs) ont été utilisées comme briques LEGO électroniques pour accomplir deux objectifs : (i) améliorer la précision des structures cristallines aux rayons X pour des petits et grands systèmes, et (ii) analyser les interactions non-covalentes dans les biomolécules. Les ELMOs sont des orbitales moléculaires strictement localisées sur des petits fragments. Pour cette raison, elles peuvent être calculées sur des petites molécules, stockées dans des bases de données, puis transférées sur des systèmes plus grands pour reconstruire

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Woińska, Magdalena. "Hirshfeld Atom Refinement of Crystal Structure and Experimental Wavefunction Fitting - Applying New Approaches in Modern Crystallography to Refinement of Diffraction Data." Doctoral thesis, 2017.

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Abstract (sommario):

Hirshfeld Atom Refinement of Crystal Structure and Experimental Wavefunction Fitting – Applying New Approaches in Modern Crystallography to Refinement of Diffraction DataTytuł w języku polskim:Udokładnienie struktury metodą atomów Hirshfelda i dopasowanie eksperymentalnej funkcji falowej – zastosowanie nowych technik współczesnej krystalografii w udokładnieniu danych dyfrakcyjnychPromotor:prof. dr hab. Krzysztof Woźniak, Wydział Chemii, Uniwersytet WarszawskiOgromny postęp w dziedzinie technik doświadczalnych z zakresu krystalografii rentgenowskiej, który dokonał się od czasów narodzin tej dzi

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Capitoli di libri sul tema "Hirshfeld Atom Refinement"

Coppens, Philip. "Space Partitioning and Topological Analysis of the Total Charge Density." In X-Ray Charge Densities and Chemical Bonding. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195098235.003.0008.

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Abstract (sommario):

In partitioning space in the analysis of a continuous charge distribution, the requirement of locality, formulated by Kurki-Suonio (Kurki-Suonio 1968, 1971; Kurki-Suonio and Salmo 1971), should be preserved. It states that density at a point should be assigned to a center in the proximity of that point. In discrete boundary partitioning schemes, the density at each point is assigned to a specific basin, while in fuzzy boundary partitioning, the density at the point may be assigned to overlapping functions centered at different locations. The least-squares formalisms described in chapter 3 impl

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