k=0 Librational Spectrum for Solid α-N2

Abstract

Articles you may be interested inComment on ''Vibron and lattice frequency shifts in the Raman spectra of solid αN2 and γN2 and librational force constants of diatomic molecular crystals'' Vibron and lattice frequency shifts in the Raman spectra of solid αN2 and γN2 and librational force constants of diatomic molecular crystals 17 For sake of simplicity, no degeneracy of eigenvalues is assumed. However, provided the largest eigenvalue is not degenerate, the splitting of '\1 into '\11 and '\12, as well as Eqs. (26), are valid anyhow. In the case of Orientation A the two largest eigen-THE JOURNAL OF CHEMICAL PHYSICS values are identical except for the sign. This makes Eq. (26c) unture, and the interpretation of Eqs. (30)-(33) less obvious; however, it might be shown that the meaning of the results is unchanged. From the formal point of view, replacement of the N bond vectors l(i) with NI2 "virtual" bonds consisting of (1(i)+ 1(i+l») would avoid trouble.An alternative description of the k=O librational spectrum of solid a-N2 is given. A variational method where the wavefunctions of the hindered rotator are expanded in terms of spherical harmonics is used. The present calculations are limited to electrostatic quadrupole-quadrupole interactions. The k=O librational frequencies are compared with the results obtained by classical lattice dynamics and another variational method as well as experiment.

Hindered internal rotations in Van der Waals molecules and molecular crystals

“…A model which is better, in principle, at describing the librations in solid N 2 and their change into hindered rotations which occurs at the a-/3 phase transition is the so-called libron model [15][16][17]. In this model it is assumed that the angular vibrations of the molecules can be expanded in a basis of free-rotor functions.…”

“…For solid N 2 several of such libron model calculations have been made [15][16][17], always using approximate empirical potentials. The most advanced one is that by Dunmore [16] who has summed the intermolecular potential over six shells (86 neighboring molecules) in the a:-N2 lattice, but has still neglected terms in the crystal potential which have nonazimuthal symmetry around the equilibrium N 2 axes (i.e., the 0 dependence of the mean-field potential).…”

“…(7) to ( 10), and to test the various libron models [15][16][17] for describing the effect of the pair correlations in (N 2)2 and looking at orientational order-disorder transitions. The mean-field "orbitals" (10) can be useful, moreover, as a basis for the full dynamical problem, instead of the free rotor basis (5).…”

Monte-Carlo Simulation of Nitrogen

“…In all these papers a Lennard-Jones atom-atom potential was used which, on the whole, does not seem to be very satisfactory, at least for the solid. On the other hand, a model employing purely quadrupolar forces has also been investigated for the solid [9][10][11][12][13] and seems to yield a better agreement with the a -ß phase transition temperature as well as with Raman active frequencies. However neither the Lennard-Jones nor the quadrupolar model seems wholly satisfactory for the lattice dynamical properties.…”

On the intermolecular potential in solid N2. II. Libronic frequencies

“…In a previous paper I (to be referred to as I) the author proposed to treat the anisotropic intermolecular potential in solid N 2 as a multipole expansion of the form where II+rl V(t~176 2 2 E Z~"t"k)lrijl-uV~ ''l') I,l' d=ll-l'l k (I) = C(l,l',J'mn y,,]+n Y~(toi) Y~,(~oj) (2) mn (The notation of this paper is consistent with that of I. In particular, we use B~ 'l';kl : AO' l ' ;k)r-kj 0 to denote the strength of an interaction at a standard density Po with nearestneighbor distance ro = 4 i. Potentials having J = I+ l' will be called "electric," regardless of origin, and all others "nonelectric."…”