[QE-users] high-temperature vc-md

[Aleksandra Oranskaia]

Dear users and developers,

Are there any tricks for running an NPT ensemble with pw.x (vc-md) for
high-temperatures? I do not have problems with 300-350-400K (reaching
minimum Etot+Ekin fluctuations after a reasonable amount of steps) but
cannot reach it for 600K. Below I show the basic input parameters used.

Thank you for any suggestions!



&CONTROL
  restart_mode = 'restart'
  calculation = 'vc-md'
  nstep = 1000
  dt = 60   ! 3fs, 1/10 of the highest vibration T
!  verbosity = 'high'
  wf_collect = .true.
  pseudo_dir = '.'
/
&SYSTEM
[all good]
  nosym = .True.
/
&ELECTRONS
[all defaut]
/
&IONS
  ion_velocities = 'default'
  tempw = 600
  ion_dynamics = 'beeman'
  pot_extrapolation = 'atomic'   ! 1st, 2nd order from prev step, no gain
  wfc_extrapolation = 'none'   ! 1st, 2nd order from prev step, no gain
! remove_rigid_rot = .True. trick for not big enough supercells
  ion_temperature = 'rescaling'
  tolp = 10
  nraise = 1
  refold_pos = .True.
/
&CELL
  cell_dynamics = 'pr'   ! Parrinello-Rahman, also Wentzcovitch 'w' is avail
!  wmass - fictitious cell mass, see default for 'pr' or 'w'
  cell_factor = 2
/

ATOMIC_SPECIES
...

ATOMIC_POSITIONS crystal
...

K_POINTS automatic
[converged grid tested to give accurate cell stresses]


-- 
Best wishes,
Al., phd candidate in chemical sciences
'I.. a universe of atoms, an atom in the universe' (Richard P. Feynman)
https://cpms.kaust.edu.sa/

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