A comment on the paper” A method of calculating volume dependence of second and third order Grüneisen parameters for MgO″by S. Chandra, Physica B 643 (2022) 414185

Different models recently used by Chandra (Physica B 643 (2022) 414185) for the volume dependence of Grüneisen parameter of MgO yield results for the third order Grüneisen parameter which are not consistent with the thermodynamic constraint at extreme compression. The results for the third order Grüneisen parameter lambda at zero-pressure can not be less than its value at extreme compression. The finding by Chandra that lambda increases with the increase in pressure is in contradiction with the results determined from fundamental studies based on the seismic data. The earlier investigations reveal that lambda decreases with the increase in pressure.