A comment on the paper entitled "A comparative study of second order and third order Gruneisen parameters for solids"

The theoretical models recently used by Chandra [Computational Condensed Matter 27 (2021) e00556] for computing the Gruneisen parameter are not valid at extreme compression but are valid at small compressions. Values of critical pressure for the validity of the Chandra models are about 24 GPa for epsilon-Fe and 3.5 GPa for NaCl. It is emphasized that the third order Gruneisen parameter assumed by Chandra to remain constant for materials under the effect of pressure is not consistent with the recent investigations. We have developed a method for determining the volume dependence of Gruneisen parameter by taking into account the pressure dependence of third order Gruneisen parameter. The results have been obtained for epsilon-Fe and NaCl which differ appreciably at high pressures from those computed by Chandra taking a constant value of third order Gruneisen parameter.