Dear Paolo Giannozzi and Ari Paavo Seitsonen
Thank you sir for your kind reply and sorry for delaying reply. I felt same thing while reading previous threads in pw_forum archives. According to suggestions given by Ari Paavo Seitsonen sir, I made all corrections and tried my level best. All trials lead to collapse of structure during Langevin dynamics. Best, Venkataramana PhD student IIT Bombay Langevin dynamics was implemented many years ago in QE, but I have never heard of anybody using it, nor seen any evidence that it works (or that it doesn't). Paolo On Mon, Aug 10, 2015 at 1:10 PM, Venkataramana Imandi <venkataramana.imandi at gmail.com <http://pwscf.org/mailman/listinfo/pw_forum>> wrote: Dear Sir/ Madam, I am using quantum espresso (version:5.1.2) for doing Langevin dynamics on Ethene molecules were kept top and bottom of silver oxide surface (total atoms: 37) running on Red Hat machine with serial and parallel process. In the output file, the coordinates of some of the atoms getting starred(***). In order to understand more about results, I tried with simple systems containing 2 Si atoms, the results shows that Langevin dynamics is working fine but the distance between two Si atoms goes on increasing (at the end of 100 md steps, the distance is 560 Angstroms). Moreover, herein Langevin dynamics is over-damped and the parameter of gamma (friction coefficient) is not mentioned anywhere in the input file description of pw.x related manual. Hence, I request you kindly suggest me how to perform Langevin calculations on my original system. Input file and starred(**) coordinates of my original system (output file) were attached. &control calculation='md', prefix='ag_eth', dt=20.D0, nstep=50, etot_conv_thr=1.0D-6, forc_conv_thr=1.0D-5, pseudo_dir = '/home/venkat/ORR1/PPS1' / &system ibrav=0, nat=37, ntyp=4, ecutwfc = 30.0, nosym=.true., occupations='smearing', smearing='m-p', degauss=0.03, tot_charge=1.0 / &electrons electron_maxstep=2000, diagonalization='david', mixing_beta = 0.3, conv_thr = 1.0D-6, scf_must_converge=.false. / &ions pot_extrapolation = 'second_order', wfc_extrapolation = 'second_order', ion_dynamics='langevin', tempw=300.D0, nraise=1 / ATOMIC_SPECIES C 12.0107 C.pbe-rrkjus.UPF H 1.00794 H.pbe-rrkjus.UPF O 15.9994 O.pbe-rrkjus.UPF Ag 107.8682 Ag.pbe-d-rrkjus.UPF CELL_PARAMETERS {angstrom} 7.8980000000 0.0000000000 0.0000000000 0.0000000000 7.8980000000 0.0000000000 0.0000000000 0.0000000000 9.7479000000 ATOMIC_POSITIONS {angstrom} C 3.674759 2.942993 -3.493103 H 4.121990 3.816735 -4.007690 H 4.121990 2.069251 -4.007690 C 2.211227 2.942993 -3.493103 H 1.763996 3.816735 -4.007690 H 1.763996 2.069251 -4.007690 O 0.000000 0.000000 -2.719012 Ag 4.448147 4.449893 -1.919012 Ag 4.448147 1.436093 -1.919012 Ag 1.437838 4.449893 -1.919012 Ag 1.437838 1.436093 -1.919012 Ag 2.942993 2.942993 0.000000 Ag 2.942993 0.000000 0.000000 Ag 0.000000 2.942993 0.000000 Ag 0.000000 0.000000 0.000000 Ag 1.437838 1.436093 1.919012 Ag 1.437838 4.449893 1.919012 Ag 4.448147 1.436093 1.919012 Ag 4.448147 4.449893 1.919012 O 0.000000 0.000000 2.719012 C 3.674759 2.942993 3.493103 H 4.121990 3.816735 4.007690 H 4.121990 2.069251 4.007690 C 2.211227 2.942993 3.493103 H 1.763996 3.816735 4.007690 H 1.763996 2.069251 4.007690 O 0.000000 5.885983 -2.719012 Ag 2.942993 5.885983 0.000000 Ag 0.000000 5.885983 0.000000 O 0.000000 5.885983 2.719012 O 5.885983 0.000000 -2.719012 Ag 5.885983 2.942993 0.000000 Ag 5.885983 0.000000 0.000000 O 5.885983 0.000000 2.719012 O 5.885983 5.885983 -2.719012 Ag 5.885983 5.885983 0.000000 O 5.885983 5.885983 2.719012 K_POINTS {gamma} A BIT of OUTPUT FILE ATOMIC_POSITIONS (angstrom) C 23.936881089 5.854758432 2.384283563 H 5.319738992 3.101932011 -2.806230409 H 5.032723666 3.366896985 -3.263624443 C -19.193958442 -0.839672619 -8.633281572 H 2.840673809 3.320817821 -3.598829264 H 2.259010092 3.506469010 -4.024573435 O 3.200827481 3.891444136 -5.674056522 Ag -2.799093034 8.698187934 0.392246441 Ag 6.216802688 0.615454519 -1.827886947 Ag -1.094861601 5.714331653 -3.826763750 Ag -0.821908140 -7.523290040 -8.937996255 Ag 7.394141127 8.391763262 7.199208896 Ag 66.2293865871065.326804153 192.584344197 Ag 4515.057117298 369.600932228 188.645687521 Ag 395.079974228 976.555500510 23.641381229 Ag -0.868373165 1.254442767 -0.725095564 Ag 0.598543920 4.290748028 1.130598433 Ag 3.451303546 0.003835176 -2.147641351 Ag 4.967046204 4.664900169 1.274377193 O 4.154896086 3.538399188 4.404896973 C 399.041692489-175.281493613-563.071390643 H 3.281002088 3.892508380 4.191590229 H 5.590682748 1.083007852 4.528641700 C -206.161786136-122.423501782 -55.021382542 H 0.246549207 5.329189077 3.491183253 H 1.659499381 1.418695757 3.087580955 O -19.384256566 28.168644116 11.242605036 Ag -75.320660159**************-197.570811974 Ag 561.119359654-921.736664610 96.273929826 O 0.652654857 4.794099697 2.674333108 O 0.725736992 1.497121799 -3.145265492 Ag ************** -53.851744674 435.559732159 Ag -59.3881630261875.893021868 -68.801534006 O 4.092070388 0.327775217 7.087480811 O 1.475113672 4.942700103 -3.552674785 Ag -847.347981606************** -58.746720826 O 5.344579864 2.986191369 5.581658260
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