[Pw_forum] cell is blowing during Langevin dynamics

[Venkataramana Imandi]

Dear all,

I am using quantum espresso (version:5.1.2) for doing Langevin dynamics on
silicon cluster (total atoms: 2) running on Red Hat machine with serial and
parallel process. If I don't use "nosym=.true." keyword in the input file,
the following error is observed, which is shown below. If I use
"nosym=.true." keyword, then super cell is blowing during Langevin
dynamics. Moreover, the coordinates of individual silicon atoms is merging
in the output file, which is shown below for one of the snapshot during
Langevin dynamics. The distance between two Silicon atoms is increasing and
at the end of 70 md steps the distance is 1152 angstroms. Kindly suggest me
what is region behind in the error. I am new user and not well aware of
Langevin dynamics in the quantum espresso software package. Input file and
coordinates of one of the snapshot are attached.

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine checkallsym (1):
     some of the original symmetry operations not satisfied
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


 &control
    calculation='md',
    dt=20.D0,
    nstep=100,
   etot_conv_thr=1.0D-5,
   forc_conv_thr=1.0D-4,
   prefix='si_lang' ,
   pseudo_dir='/home/venkat/ORR1/PPS1'
 /
 &system
    ibrav= 2,
    celldm(1)=10.18,
     nat=2,
     ntyp= 1,
    ecutwfc = 8.0,
    nosym=.true.
 /
 &electrons
  electron_maxstep=2000,
   diagonalization='david',
    conv_thr =  1.0e-5,
    mixing_beta = 0.3,
   scf_must_converge=.false.
 /
 &ions
pot_extrapolation = 'second_order',
wfc_extrapolation = 'second_order',
ion_dynamics='langevin',
refold_pos=.true.
tempw=300.D0,
nraise=2
 /
ATOMIC_SPECIES
 Si  28.086  Si.pz-vbc.UPF
ATOMIC_POSITIONS {alat}
 Si -0.123 -0.123 -0.123
 Si  0.123  0.123  0.123

K_POINTS {automatic}
 1 1 1 0 0 0

one snapshot during Langevin dynamics

ATOMIC_POSITIONS (alat)
Si     210.463044756 215.584817447-144.659285586
Si    -210.463044756-215.584817447 144.659285586

Best,
Venkataramana
PhD student
IIT Bombay
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