''Inelastic Neutron Scattering and Periodic Density Functional Studies of Hydrogen Bonded Structures''

Hudson, Bruce S.

Syracuse University (United States)

关键词: Hydrogen Bonding;    Eigenvectors;    Spectra;    Line Widths;    08 Hydrogen;   

DOI  :  10.2172/833891
RP-ID  :  1
RP-ID  :  FG02-01ER15245
RP-ID  :  833891

美国|英语

来源: UNT Digital Library

【 摘 要 】

This project is directed at a fundamental understanding of hydrogen bonding, the primary reversible interaction leading to defined geometries, networks and supramolecular aggregates formed by organic molecules. Hydrogen bonding is still not sufficiently well understood that the geometry of such supramolecular aggregates can be predicted. In the approach taken existing quantum chemical methods capable of treating periodic solids have been applied to hydrogen bonded systems of known structure. The equilibrium geometry for the given space group and packing arrangement were computed and compared to that observed. The second derivatives and normal modes of vibration will then be computed and from this inelastic neutron scattering (INS) spectra were computed using the normal mode eigenvectors to compute spectral intensities. Appropriate inclusion of spectrometer line width and shape was made in the simulation and overtones, combinations and phonon wings were be included. These computed spectra were then compared with experimental results obtained for low-temperature polycrystalline samples at INS spectrometers at several facilities. This procedure validates the computational methodology for describing these systems including both static and dynamic aspects of the material. The resulting description can be used to evaluate the relative free energies of two or more proposed structures and so ultimately to be able to predict which structure will be most stable for a given building block.