<div dir="ltr"><div>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). <br><br></div>Paolo<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Aug 10, 2015 at 1:10 PM, Venkataramana Imandi <span dir="ltr"><<a href="mailto:venkataramana.imandi@gmail.com" target="_blank">venkataramana.imandi@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>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.<a href="tel:7479000000" value="+17479000000" target="_blank">7479000000</a><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><div><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<br><br><br> <br>Best,<br>Venkataramana<br>PhD student<span class="HOEnZb"><font color="#888888"><br><br clear="all"><br>-- <br><div>venkataramana</div>
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