[Pw_forum] temperature rescaling for vc-md

[Huiqun Zhou]

Hi,

I'm trying to run a vc-md simulation of a supercell with 80 atoms at 300 K and 20 GPa,
but the SCF convergence is always failed to reach after 20 or so ion steps no matter 
how I change mixing_beta from 0.5 to 0.05. One thing I noticed is that the temperature
controling may be not in effect as the temperature remains as high as 6 digits. I used 
the 'rescaling' , the only setting available for vc-md, for ion_temperature, the default 
100.0 for tolp. 

Below is part of my input file, any comments are welcome. I would also like to know
which source file I need to look at for the rescaling function. 

The same system is running without any problem using CP dynamics in VASP and 
CASTEP. 

 &control
    calculation = 'vc-md',
    restart_mode = 'from_scratch',
    prefix = 'mgsio3',
    tstress = .true.,
    tprnfor = .true.,
    pseudo_dir = '/home/hqzhou/qe_pseudo/',
    outdir = '/gpfsTMP/hqzhou/tmp/'
    wf_collect = .true.
    nstep = 100
    dt = 20.0
 /
 &system
    !ibrav = 0
    !celldm(1) = 0.0
    ibrav = 14
    celldm(1) = 18.0484, celldm(2) = 1.0322, celldm(3) = 0.7221
    celldm(4) = 0.0, celldm(5) = 0.0, celldm(6) = 0.0
    nat = 80, ntyp = 3,
    ecutwfc = 40.0, ecutrho = 400.0
    nspin = 1
    nosym = .true.
    occupations = 'fixed'
 /
 &electrons
    electron_maxstep = 200
    diagonalization = david
    mixing_mode = 'plain'
    mixing_beta = 0.1
    conv_thr = 1.0d-8
 /
 &ions
    ion_dynamics = 'beeman'
    pot_extrapolation = 'second_order'
    wfc_extrapolation = 'second_order'
    upscale = 100.0
    ion_temperature = 'rescaling'
    tempw = 300.0
    refold_pos = .true.
 /
 &cell
    cell_dynamics = 'pr'
    press = 200.0
    !wmass = 0.05
    cell_factor = 1.6
    press_conv_thr = 0.2
 /
......

Thanks in advance.

zhou huiqun
@earth sciences, nanjing university, china

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