Properties of solid and gaseous hydrogen, based upon anisotropic pair interactions

Charge overlap effects and the validity of the multipole results for first-order molecule-molecule interaction energies. Formalism and an application to H2-H2

“…The result given by (26) agrees with that obtained previously by Karl et al [20], whereas their result corresponding to (27) appears to be in error.…”

“…It is clear that the second-order Coulomb energy is not negligible with respect to the first-order Coulomb energy for values of R associated with the results of tables 2-5. For example, when R=8 the London dipole-dipole dispersion energy (36) is of the same order of magnitude as the quadrupolequadrupole energy E2, 2 (1) In some applications [27,28,34] the total interaction energy is represented as the sum of the orientation averaged interaction energy, E(R), and the orientation dependent part of the interaction energy, E(R, f~), which is made up of exchange and Coulomb parts Ex(R, f~) and Eo(R, f~) respectively. The Coulomb orientation dependent part of the interaction energy is usually represented by angular dependent parts of truncated multipole expansions of the first and second-order Coulomb energies.…”

“…Using (27) and the method and parameters discussed in [20], the expression for the molecular hexadecapole of H a as a function of R around the equilibrium value of R = 1.4 is given by…”

Frequency dependence of Raman-active phonons in solid HCP hydrogen on ortho-para concentration and temperature

“…The isotropic potential was earlier taken to be of the Lennard-Jones form, 2 but more recent work shows that this potential is too hard in the core; a more physical representation is found by combining an exponential repulsive potential in the core with a long-range attractive potential due to dispersive forces. 4 Hydrogen crystallizes in the hexagonal-closed-packed (hcp) lattice when grown from the bulk at -14 K (D2 at -19 K). The pure p-H2 solid remains hcp to T = 0 K. Pure o-H2 has a transition into an orientationally ordered phase with the Pa3 structure* (molecular centers of mass sit on an fcc lattice) at T = Tc -~ 2.8 K for zero pressure.…”

The Search for Quantum Liquid Crystals

“…One might approximate v(r) by v( p ) , u ( r ) by u( p ) , and correspondingly, P'I' and P(2' by = P'l'(p1)P'l'(p2)g(p1 , p 2 ) x 2 ( z l ) x 2 (~2 ) (10) For every choice of the trial wave function, the task of evaluating E reduces then to a determination of P'''(p1) and g ( p l , p z ) .…”