<div dir="ltr"><br clear="all">Dear all,<br><br>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.<br><br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>     Error in routine checkallsym (1):<br>     some of the original symmetry operations not satisfied<br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br><br><br> &control<br>    calculation='md',<br>    dt=20.D0,<br>    nstep=100,<br>   etot_conv_thr=1.0D-5,<br>   forc_conv_thr=1.0D-4,<br>   prefix='si_lang' ,<br>   pseudo_dir='/home/venkat/ORR1/PPS1'<br> /<br> &system<br>    ibrav= 2,<br>    celldm(1)=10.18,<br>     nat=2,<br>     ntyp= 1,<br>    ecutwfc = 8.0,<br>    nosym=.true.<br> /<br> &electrons<br>  electron_maxstep=2000,<br>   diagonalization='david',<br>    conv_thr =  1.0e-5,<br>    mixing_beta = 0.3,<br>   scf_must_converge=.false.<br> /<br> &ions<br>pot_extrapolation = 'second_order',<br>wfc_extrapolation = 'second_order',<br>ion_dynamics='langevin',<br>refold_pos=.true.<br>tempw=300.D0,<br>nraise=2<br> /<br>ATOMIC_SPECIES<br> Si  28.086  Si.pz-vbc.UPF<br>ATOMIC_POSITIONS {alat}<br> Si -0.123 -0.123 -0.123<br> Si  0.123  0.123  0.123<br><br>K_POINTS {automatic}<br> 1 1 1 0 0 0<br><br>one snapshot during Langevin dynamics<br><br>ATOMIC_POSITIONS (alat)<br>Si     210.463044756 215.584817447-144.659285586<br>Si    -210.463044756-215.584817447 144.659285586<br><br>Best,<br>Venkataramana<br>PhD student<br>IIT Bombay<br><br><br>
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