Vibrons and phonons in solid hydrogen at megabar pressures

Raman and infrared active vibrons and phonons in the solid molecular hydrogen at megabar pressures have been studied by the first-principles band theoretical calculations assuming the hcl, lattice of the centers of the molecules. The frequencies of the out-of-phase stretching motion of the two molecules in the unit cell are higher than those of the in-phase stretching motion. Pressure dependence of the frequency of a phonon-like mode, which lies in 1300 cm(-1) similar to 1900 cm(-1) at pressures 70 GPa similar to 200 GPa, is in good agreement with the recent experiments. Our results suggest that the lattice of the solid hydrogen remains hcp beyond the phase transition at 150 GPa.