[QE-users] Query Regarding Car-Parrinello Molecular Dynamics Convergence

[Vinay Maithani]

Dear Quantum Espresso Community,

I am currently working on CPMD calculations. After running vc-cp (NPT) for
135 picoseconds (ps), (I have attached the image for reference) I have
observed that although the potential energy of the system Etot (E_DFT) and
econs (E_DFT + K_NUCLEI) are not converging but the constant of motion of
CP lagrangian, Econt (E_DFT + K_IONS + K_ELECTRONS) remains constant.

In Prof Marzari’s recent paper (
https://www.nature.com/articles/s41524-022-00948-8.), I have found that,
for meaningful statistical data etot and econs should be converge,
specifically, I am curious about the necessity for etot and econs to
converge and what should be convergence criteria. How long, in picoseconds,
should I run these simulations to reasonably expect convergence,
particularly in the context of etot and econs?

Your guidance on this matter would be greatly appreciated.

Best regards,

Vinay Maithani
IIT Kharagpur
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