[QE-users] Oscillating volume in VC-MD

[Andrii Shyichuk]

Dear Users,

I am running a VC-MD calculation where the cell volume oscillates in a 
nice sinusoidal way, with the period of about 250 fs.
The oscillations are in the range of 99.5-101.5% of the initial volume 
for 300K, and within 99-102.5% for 500K.

That happens both with 5 fs (dt=103.353) and 0.5 fs (dt=10.33534) time 
steps.
The tolp was 10 in the first case and 2 in the second case.

I use ion_temperature = 'rescaling',  cell_dynamics = 'pr', ion_dynamics 
= 'beeman' and nraise = 1.

I've tried searching the mailing archive and found nothing relevant.

Is it normal? Shouldn't the volume converge to a certain value?


Thank you in advance.
Best regards.
Andrii Shyichuk, University of Wrocław