Pressure dependence of the elastic stiffness constants of alkali metals

Using a local Heine-Abarenkov model potential and the perturbational formalism, the elastic shear constants C 44 and C'=(C 11 -C 12 )/2 of alkali metals subject to pressure are derived theoretically, and the pressure derivatives of the elastic stiffness constants dB/dP, dC 44 /dP and dC'/dP arising from volume changes are calculated. The values of the elastic constants increase with increasing pressure, and those of the pressure derivatives dC 44 /dP and dC'/dP decrease with increasing pressure.