Artykuł w czasopiśmie
Brak miniatury
Licencja
ClosedAccessDostęp zamknięty
 

A combined model of electron density and lattice dynamics refined against elastic diffraction data. Thermodynamic properties of crystalline L-alanine

Uproszczony widok
cris.lastimport.scopus2024-02-12T20:16:24Z
dc.abstract.enThermodynamic stability is an essential property of crystalline materials, and its accurate calculation requires a reliable description of the thermal motion - phonons - in the crystal. Such information can be obtained from periodic density functional theory (DFT) calculations, but these are costly and in some cases insufficiently accurate for molecular crystals. This deficiency is addressed here by refining a lattice-dynamics model, derived from DFT calculations, against accurate high-resolution X-ray diffraction data. For the first time, a normal-mode refinement is combined with the refinement of aspherical atomic form factors, allowing a comprehensive description and physically meaningful deconvolution of thermal motion and static charge density in the crystal. The small and well diffracting l-alanine system was used. Different lattice-dynamics models, with or without phonon dispersion, and derived from different levels of theory, were tested, and models using spherical and aspherical form factors were compared. The refinements indicate that the vibrational information content in the 23K data is too small to study lattice dynamics, whereas the 123K data appear to hold information on the acoustic and lowest-frequency optical phonons. These normal-mode models show slightly larger refinement residuals than their counterparts using atomic displacement parameters, and these features are not removed by considering phonon dispersion in the model. The models refined against the 123K data, regardless of their sophistication, give calculated heat capacities for l-alanine within less than 1 calmol-1K-1 of the calorimetric measurements, in the temperature range 10-300K. The findings show that the normal-mode refinement method can be combined with an elaborate description of the electron density. It appears to be a promising technique for free-energy determination for crystalline materials at the expense of performing a single-crystal elastic X-ray diffraction determination combined with periodic DFT calculations.
dc.affiliationUniwersytet Warszawski
dc.contributor.authorHoser, Anna
dc.contributor.authorSovago, Ioana
dc.contributor.authorMadsena, Anderso
dc.date.accessioned2024-01-24T17:17:59Z
dc.date.available2024-01-24T17:17:59Z
dc.date.issued2020
dc.description.financePublikacja bezkosztowa
dc.description.volumeA76
dc.identifier.doi10.1107/S205327331901355X
dc.identifier.urihttps://repozytorium.uw.edu.pl//handle/item/101464
dc.languageeng
dc.pbn.affiliationchemical sciences
dc.relation.ispartofActa Crystallographica Section A: Foundations and Advances
dc.relation.pages32-44
dc.rightsClosedAccess
dc.sciencecloudnosend
dc.subject.encharge density
dc.subject.enmodeling Villum Fonden VKR023450 Anders Østergaard Madsen
dc.subject.enthermal motion
dc.subject.enthermodynamics
dc.titleA combined model of electron density and lattice dynamics refined against elastic diffraction data. Thermodynamic properties of crystalline L-alanine
dc.typeJournalArticle
dspace.entity.typePublication