The structure in highly compressed hydrogen and the orientational transitionF. Grazzi1, M. Moraldi2, 3 and L. Ulivi1, 3
1 ISC-CNR - via della Madonna del piano, I-50019 Sesto Fiorentino, Italy
2 Dipartimento di Fisica, Università di Firenze via G. Sansone 1, I-50019 Sesto Fiorentino, Italy
3 INFM, Unità di Firenze - Via Giovanni Sansone 1, I-50019 Sesto Fiorentino, Italy
received 2 June 2004; accepted in final form 7 October 2004
published online 29 October 2004
A calculation of the rotational S0(0) frequencies in high-pressure solid para-hydrogen is performed. Convergence of the perturbative series at high density is demonstrated by the calculation of second- and third-order terms. The results of the theory are compared with the available experimental data to derive the density behaviour of structural parameters. In particular, a strong increase of the value of the lattice constant ratio c/a and of the internuclear distance is determined. Also a decrease of the anisotropic intermolecular potential is observed which is attributed to charge transfer effects. The structural parameters determined at the phase transition may be used to calculate quantum properties of the rotationally ordered phase.
62.50.+p - High-pressure and shock wave effects in solids and liquids.
78.30.-j - Infrared and Raman spectra.
34.20.-Gj - Atomic and molecular collision processes and interaction: Intermolecular and atom-molecule potentials and forces.
© EDP Sciences 2004