<div dir="ltr"><pre>Dear Paolo Giannozzi sir,</pre><br><br>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.<br><br><div>Best,<br></div><div>Venkataramana<br></div><div>PhD student<br></div><div>IIT Bombay<br></div><div><br><pre>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 <
<a href="http://pwscf.org/mailman/listinfo/pw_forum" target="_blank">venkataramana.imandi at gmail.com</a>> wrote:
</pre><br><br>Dear Sir/ Madam,<br><br>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.<br><br> &control<br> calculation='md',<br> prefix='ag_eth',<br> dt=20.D0,<br> nstep=50,<br> etot_conv_thr=1.0D-6,<br> forc_conv_thr=1.0D-5,<br> pseudo_dir = '/home/venkat/ORR1/PPS1'<br> /<br>&system<br> ibrav=0,<br> nat=37,<br> ntyp=4,<br> ecutwfc = 30.0,<br> nosym=.true.,<br> occupations='smearing',<br> smearing='m-p',<br> degauss=0.03,<br> tot_charge=1.0<br>/<br>&electrons<br> electron_maxstep=2000,<br> diagonalization='david',<br> mixing_beta = 0.3,<br> conv_thr = 1.0D-6,<br> scf_must_converge=.false.<br>/<br>&ions<br>pot_extrapolation = 'second_order',<br>wfc_extrapolation = 'second_order',<br>ion_dynamics='langevin',<br>tempw=300.D0,<br>nraise=1<br> /<br>ATOMIC_SPECIES<br>C 12.0107 C.pbe-rrkjus.UPF<br>H 1.00794 H.pbe-rrkjus.UPF<br>O 15.9994 O.pbe-rrkjus.UPF<br>Ag 107.8682 Ag.pbe-d-rrkjus.UPF<br><br>CELL_PARAMETERS {angstrom}<br>7.8980000000 0.0000000000 0.0000000000<br>0.0000000000 7.8980000000 0.0000000000<br>0.0000000000 0.0000000000 9.7479000000<br><br>ATOMIC_POSITIONS {angstrom}<br><br> C 3.674759 2.942993 -3.493103<br> H 4.121990 3.816735 -4.007690<br> H 4.121990 2.069251 -4.007690<br> C 2.211227 2.942993 -3.493103<br> H 1.763996 3.816735 -4.007690<br> H 1.763996 2.069251 -4.007690<br> O 0.000000 0.000000 -2.719012<br>Ag 4.448147 4.449893 -1.919012<br>Ag 4.448147 1.436093 -1.919012<br>Ag 1.437838 4.449893 -1.919012<br>Ag 1.437838 1.436093 -1.919012<br>Ag 2.942993 2.942993 0.000000<br>Ag 2.942993 0.000000 0.000000<br>Ag 0.000000 2.942993 0.000000<br>Ag 0.000000 0.000000 0.000000<br>Ag 1.437838 1.436093 1.919012<br>Ag 1.437838 4.449893 1.919012<br>Ag 4.448147 1.436093 1.919012<br>Ag 4.448147 4.449893 1.919012<br> O 0.000000 0.000000 2.719012<br> C 3.674759 2.942993 3.493103<br> H 4.121990 3.816735 4.007690<br> H 4.121990 2.069251 4.007690<br> C 2.211227 2.942993 3.493103<br> H 1.763996 3.816735 4.007690<br> H 1.763996 2.069251 4.007690<br> O 0.000000 5.885983 -2.719012<br>Ag 2.942993 5.885983 0.000000<br>Ag 0.000000 5.885983 0.000000<br> O 0.000000 5.885983 2.719012<br> O 5.885983 0.000000 -2.719012<br>Ag 5.885983 2.942993 0.000000<br>Ag 5.885983 0.000000 0.000000<br> O 5.885983 0.000000 2.719012<br> O 5.885983 5.885983 -2.719012<br>Ag 5.885983 5.885983 0.000000<br> O 5.885983 5.885983 2.719012<br><br>K_POINTS {gamma}<br><br></div>A BIT of OUTPUT FILE <br><br>ATOMIC_POSITIONS (angstrom)<br>C 23.936881089 5.854758432 2.384283563<br>H 5.319738992 3.101932011 -2.806230409<br>H 5.032723666 3.366896985 -3.263624443<br>C -19.193958442 -0.839672619 -8.633281572<br>H 2.840673809 3.320817821 -3.598829264<br>H 2.259010092 3.506469010 -4.024573435<br>O 3.200827481 3.891444136 -5.674056522<br>Ag -2.799093034 8.698187934 0.392246441<br>Ag 6.216802688 0.615454519 -1.827886947<br>Ag -1.094861601 5.714331653 -3.826763750<br>Ag -0.821908140 -7.523290040 -8.937996255<br>Ag 7.394141127 8.391763262 7.199208896<br>Ag 66.2293865871065.326804153 192.584344197<br>Ag 4515.057117298 369.600932228 188.645687521<br>Ag 395.079974228 976.555500510 23.641381229<br>Ag -0.868373165 1.254442767 -0.725095564<br>Ag 0.598543920 4.290748028 1.130598433<br>Ag 3.451303546 0.003835176 -2.147641351<br>Ag 4.967046204 4.664900169 1.274377193<br>O 4.154896086 3.538399188 4.404896973<br>C 399.041692489-175.281493613-563.071390643<br>H 3.281002088 3.892508380 4.191590229<br>H 5.590682748 1.083007852 4.528641700<br>C -206.161786136-122.423501782 -55.021382542<br>H 0.246549207 5.329189077 3.491183253<br>H 1.659499381 1.418695757 3.087580955<br>O -19.384256566 28.168644116 11.242605036<br>Ag -75.320660159**************-197.570811974<br>Ag 561.119359654-921.736664610 96.273929826<br>O 0.652654857 4.794099697 2.674333108<br>O 0.725736992 1.497121799 -3.145265492<br>Ag ************** -53.851744674 435.559732159<br>Ag -59.3881630261875.893021868 -68.801534006<br>O 4.092070388 0.327775217 7.087480811<br>O 1.475113672 4.942700103 -3.552674785<br>Ag -847.347981606************** -58.746720826<br>O 5.344579864 2.986191369 5.581658260</div>