[Pw_forum] Using energy/wavefunctions from last calculation for next calculation

Mitul Mundra mitulm at iitk.ac.in
Sat Sep 28 15:31:46 CEST 2013

I am a beginner in Quantum Espresso and I am trying to do geometrical
optimization using Quantum Espresso. Instead of using calculation =
'relax', I wish to use my own optimizer by using calculation = 'scf' and
then do iterations. It is working fine but I wish to reduce the computation
time. Therefore, I was trying to use the energy or wavefunction obtained
from my last scf calculation as the initial guess for my next scf
calculation because I am moving the atoms of my system  infinitesimally.
The problem I am facing is that I can only give the coordinates of my atoms
as input and then QE does its own calculations, therefore, I do not get the
opportunity to provide a good initial guess to it (which would be
energy/wavefunction from my last calculation). Is there a way to provide
the initial guess to QE?
A way in which it could work can be to set *wf_collect = .TRUE.* (which
collects the wavefunction in the tmp folder) and then setting restart mode
= 'restart' for next calculation which I think would use the wavefunctions
from last calculation but I am not able to see clearly how these things can
be executed?
Also, what should be force and energy tolerance values for a Si system for
convergence of a geometrical optimization problem to reduce the number of

Mitul Mundra
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