[Pw_forum] Cannot reach the target temperature in vc-md calculation using pwscf; and where I can find the updated velocities?

[Tian Lan]

Dear all,

I am running vc-md of a cuprite structure with 2 by 2 by 2 supercell. When
I set the tempw=300, it does converge but the equilibrium temperature seems
to be only 190K. It starts from 280 and all the way down to 190K and
converges there. Actually I did not find many controls on it, below is what
my current setups for &ions and &cells.

I kept trying different setups, but has little effect, for example, I tried
different 'dt' from 20 to 50, different 'ion_temperature' choices, 'tolp'
or 'nraise'. I also used a primitive cell, the actual temperature can be
only 108K or so. Therefore, I am not sure whether it has something to do
with the cell size, or the temperature calibration issue, or some setup
would substantially influence the temperature control.

 &ions
    tempw=300,
    ion_temperature= 'rescaling',
    tolp=20,
    nraise=1,
    pot_extrapolation='second-order',
    wfc_extrapolation='second-order',
 /
 &cell
    cell_dynamics = 'pr' ,
    press = 0.00
 /
Besides of it, I have a stupid question because I did not find any
information about the atom velocities. I only find updated coordinates and
forces in .out file. In .save folders, I did not find anything either. My
control icons for print are as follows:

    disk_io='high'
!    wf_collect=.TRUE.
    pseudo_dir = '.',
    outdir='\temp'
    tstress =.true.,
    tprnfor =.true.,

Thank you in advance if you have any idea about these.
Best Regards,
Tian
-- 
Lan, Tian
Ph.D. Candidate, Department of Applied Physics and Materials Science
California Institute of Technology,
Caltech M/C 138-78, Pasadena, CA, 91125
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