  We investigate the effect of nuclear quantum effects (NQEs) of hydrogen atoms
on the elasticity of ice VII at high pressure and ambient temperature
conditions using ab initio path-integral molecular dynamics (PIMD)
calculations. We find that the NQEs of hydrogen contributes to the transition
of ice VII from a static disordered structure to a dynamically disordered
structure at pressures exceeding 40 GPa. This transition is marked by a
discontinuous increase of the elastic constants. Comparison of ab initio
molecular dynamics and PIMD calculations reveal that NQEs increase the elastic
constants of ice by about 20% at 70 GPa and 300 K.
