PRESSURE EFFECTS ON HYDROGEN-BONDING IN THE DISORDERED PHASE OF SOLIDHBR

Nature and stability of the disordered phase I of solid HBr under pres sure were investigated using the ab initio molecular dynamics method. A detailed study of the response to pressure of the orientational dist ribution and the reorientational and vibrational dynamics showed that phase I can be described as a rotator phase with fluctuating hydrogen bonds up to pressures well over 10 GPa. The remarkable stability of ph ase I under pressure is explained in terms of more efficient packing o f hydrogen-bonded molecules in disordered structures. We predict that the disorder at higher densities leads to cooperative proton-transfer dynamics.