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Bond valence sum: a new soft chemical constraint for RMCProfile
Author(s) -
Norberg Stefan T.,
Tucker Matthew G.,
Hull Stephen
Publication year - 2009
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889809004981
Subject(s) - reverse monte carlo , valence (chemistry) , neutron diffraction , scattering , bond length , monte carlo method , chemical bond , crystallography , diffraction , chemistry , materials science , molecular physics , crystal structure , physics , optics , mathematics , statistics , organic chemistry
The implementation of a new soft chemical constraint for the reverse Monte Carlo (RMC) program RMCProfile , based on bond valence sum (BVS) calculations, is described and its advantages for the analysis of `total scattering' diffraction data collected from disordered crystalline systems discussed. The inclusion of the BVS formalism proves particularly valuable in the early stages of the RMC fitting procedure, by avoiding the formation of regions containing chemically unreasonable local configurations which can become frozen in. Furthermore, this approach provides the fitting procedure with additional chemical information to differentiate between cation species that share the same crystallographic sites within the averaged unit cell and possess similar neutron scattering lengths. These issues are illustrated using total neutron scattering data collected at room temperature on the oxide‐ion conductor Zr 2 Y 2 O 7 and the nonlinear optical material KTiOPO 4 .