[QE-users] What is the difference between Pressure of Nuclei and Pressure Total in CPMD ?

[Nam Tran]

Dear QE users and experts,

I am using CPMD in Quantum Espresso to equilibrium a system with an external pressure of 2 GPa. I used variable-cell molecular dynamic (calculation ='vc-cp' and press = 20), the high of the cell 'z' was allowed to change to maintain the pressure. The target is to reproduce some of the calculation in the following paper: https://pubs.acs.org/doi/abs/10.1021/jp206135k

I found that two type of pressure are printed in the output file, Pressure of Nuclei and Pressure Total. The pressure of nuclei is relatively close to the external pressure while the total one is fluctuate a lot.

What is the meaning and difference between them ?.

Best regards
Nam Tran


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