Ab-initio study of C2/c, Cmca-12, Pbcn and P6122 phases of solid hydrogen

We investigate structural, electronic, phononic and mechanical properties of the C2/c, Cmca-12, Pbcn and P6122 phases of solid hydrogen in the 100-300 GPa pressure region using ab-initio methods. The computed structural parameters, PV-equation of states (EOSs), electronic and phononic properties show a good agreement with the earlier values. By computing second-order elastic constants, we establish the mechanical stability of all phases in the studied pressure region and these values were used to compute the average sound velocities and Debye temperatures. All these quantities exhibit usual pressure behaviour. Further, we found that at 100 GPa, C2/c and P6122 phases are dynamically unstable and Pbcn phase is unstable in the entire pressure region. The effect of vdW corrections is also tested for C2/c and P6122 phases at 100 GPa.