[QE-users] How to choose appropriate emass and dt in cp.x with occupations = 'ensemble'?

[Ms.Shruthi A S]

Hi all,
I'm performing Car-Parrinello MD simulations using Quantum ESPRESSO’s cp.x, and my system is metallic , so I’ve set:

occupations = 'ensemble'
However, I’m unclear about how to properly choose the following parameters:
1. emass

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What is the correct way to set emass in the context of ensemble occupations?
  *
How does the use of Fermi–Dirac smearing (via degauss) influence the choice of emass?
  *
Are there any convergence tests or stability checks that I should monitor when adjusting emass?

2. dt (time step)

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How should I choose dt in relation to emass to ensure numerical stability?
  *
Should dt be smaller when emass is low or when using ensemble occupations?

If anyone has recommendations, rules of thumb, or references (e.g., papers or documentation examples), that would be incredibly helpful.
Thanks in advance!


Thanks and Regards
Shruthi A S
Research Scholar,
Nanoelectronics Research Laboratory
Department of Electronics,
Amrita Vishwa Vidyapeetham
Amrita School of Engineering-Bangalore
Ph +918951110185
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