Tentative Study of Proton Dynamics in Crystals with Quasi-linear H-bonds

Tentative Study of Proton Dynamics in Crystals with Quasi-linear H-bonds 

A qualitative description of the structural and spectroscopic properties of H-bonded crystals requires the use of a simple two-mode linear model (9.1). 

Here A and B are heavy molecular fragments and their internal structure is not specified in detail now. The centers of gravity of the B, A and H particles lie on the same straight line. The proton coordinate (s) is measured from the center of gravity ( ) of the whole system (9.1). The distance between the terminal atoms (rather than between the centers of gravity of fragments B and A) is usually taken as the coordinate R. Typical values of the reduced masses (m and M) and characteristic frequencies (v g and v ) corresponding to the s and R coordinates are m 1 and M 10 a.u. 1000 and Vg 200 cnr.  

The R coordinate is a typical example of a so-called promoting mode [7]. It does not change (B = A) or very slightly changes (B A) when the bridging proton shifts from A to B. However, it appreciably changes in the transition state and thus modifies the height of the potential barrier. 

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