how to estimate the pressure deviation from LDA overbinding

[lqzhang]

Dear all:

I work on mgo melts and I used LDA in vasp calculation, which can cause overbinding, thus pressure deviation(P_emp). I tried to estimate the P_emp. Based on one paper, P_emp should be calculated as following:

P_emp= - P_s(V_exp; E_cut=600 ev)

V_exp is the experimental zero-pressure volume of the solid phase at static conditions. P_s is the static pressure of corresponding crystalline phase computed at high cutoff (like 600 ev).

Based on the mgo crystal structure POSCAR file posted by the forum administrator, I did NVT ensemble molecular dynamic simulation for 2 ps at 300 K using Encut=600 ev. I found the external pressure fluctuated in the range of -4 ~ -6.5 GPa, which has the magnitude much larger than the data reported in the paper. Could I know where could be wrong in my calculation? Thank you very much.

[lqzhang]

My problem was solved. In fact, there is nothing wrong in my calculation. The different pseudopotential I used caused the problem. When using ultra-soft pseudopotential, the value is smaller.