Rigid unit mode model

Dove MT (1993) Introdnction to lattice dynamics. Cambridge University Press, Cambridge Dove MT, Giddy AP, Heine V (1993) Rigid unit mode model of displacive phase transitions in framework silicates. Trans Am Crystallogr Assoc 27 65-74... 

Hammonds KD, Heine V, Dove MT (1997b) Insights into zeolite behavior from the rigid unit mode model. Phase Trans 61 155-172... 

Rigid unit mode model of displacive phase transition in framework... 

APPLICATIONS OF THE RIGID UNIT MODE (RUM) MODEL Displacive phase transitions... 

Inelastic neutron scattering experiments have shown that strong structural similarities exist between P-cristobalite and amorphous silica, but also HP-tridymite over a length scale up to 1.0 nm. This has been interpreted in terms of the internal flexibility of the Si04 tetrahedra, as deduced from the rigid unit mode (RUM) model (see Appendix B). This internal flexibility will distort the local structure of the crystalline phase such as P-cristobalite to achieve a disorder similar to that found in the amorphous phases, silica gel, or silica glass. 

To study the vibrational energy relaxation of the amide I mode in N-methylacetamide, we employed the OPLS all-atom force field to model the solute and the flexible simple-point-charge (SPC) water modeF with doubled hydrogen masses to model the solvent D2O. To investigate the photoinduced heat transfer in photoswitchable peptides, we used the GROMOS96 united atom force field 43al. Additional force field parameters for the azobenzene unit were derived from density functional theory as described in Ref. [32]. We employed a united-atom modeP to describe the DMSO solvent, the SPC modeP to describe water, and the rigid all-atom model of Ref [57] to describe the chloroform solvent. 

Recent numerical experiments by the method of molecular dynamics have shown that, for a chain model consisting of particles joined by ideally rigid bonds, the Van der Waals interactions of chain units cause only a little change in the dependence of relaxation times on the wave vector of normal modes of motions, i.e. in the character and shape of the relaxation spectrum. It was found that for the model chain the important relationship... 

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