Dear Deepak!<br><br>There no cell parameter in your input. You have to take the experimental value of the lattice constant available or dig out some paper in which the relevant calculations are done. See the INPUT_PW.txt in DOC folder of espresso distribution. The meaning of parameters are very clearly mentioned there. And next time please mention your affiliation so that we should know whom we are interacting with. <br>
<br><div class="gmail_quote">On Wed, Aug 3, 2011 at 11:19 PM, dipak thakur <span dir="ltr"><<a href="mailto:deepak.p.thakur@gmail.com">deepak.p.thakur@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
I am nobe to quantum espresso and using supercell for first time.<br>Can any one help me in understanding few things regarding the supecell determination?<br><br>The following is a typical input file I am using (copied from one of the earlier post).<br>
<pre>CONTROL<br> title = 'Graphene mono layer'<br> calculation = "relax" ,<br> restart_mode = 'from_scratch' ,<br> outdir='/home/usuarios/baldini/espresso-4.2.1/tmp/' ,<br> pseudo_dir = '/home/usuarios/baldini/espresso-4.2.1/pseudo' ,<br>
etot_conv_thr = 1.0E-4 ,<br> forc_conv_thr = 1.0D-3 ,<br> nstep=50,<br> dt=40,<br> prefix='1MLG_Ti_H2',<br>/<br>&SYSTEM<br> ibrav = 0.,<br>
ntyp = 2 ,<br> nat = 33 ,<br> ecutwfc = 50.0 ,<br> ecutrho = 400.0,<br>/<br>&ELECTRONS<br> electron_maxstep = 300.,<br> conv_thr = 1.0d-8 ,<br>
mixing_mode = 'plain',<br> mixing_beta = 0.5,<br> diagonalization = 'cg' ,<br> diago_cg_maxiter = 50,<br>/<br>&IONS<br>/<br>CELL_PARAMETERS<br>16.12131954 9.383047808 0.0000000<br>
0.00000000 18.658162370 0.0000000<br>0.0000000 0.0000000 56.6893424<br>ATOMIC_SPECIES<br>C 12.0107 C.pbe-van_ak.UPF<br>Ti 47.8670 Ti.pbe-sp-van_ak.UPF<br>ATOMIC_POSITIONS angstrom<br>C 2.89163 7.40219 1.8862<br>
C 3.59292 8.63832 1.8826<br>C 3.60349 6.16702 1.8884<br>C 5.0186 8.64501 1.8612<br>C 5.0215 6.16598 1.8904<br>C 5.73302 7.40522 1.8718<br>
C 1.47184 7.39616 1.891<br>C 2.89112 9.87066 1.886<br>C 2.89471 4.93264 1.8916<br>C 5.73319 9.8885 1.8612<br>C 5.73643 4.9413 1.8924<br>
C 7.16348 7.41203 1.882<br>C 1.47474 4.9269 1.8924<br>C 0.762281 8.62783 1.8946<br>C 0.763134 6.16172 1.8914<br>C 1.4715 9.86335 1.8934<br>
C 3.60341 11.1095 1.8868<br>C 5.02124 11.1239 1.882<br>C 3.60512 3.70156 1.8932<br>C 5.02645 3.70789 1.891<br>C 7.87807 8.65532 1.8816<br>
C 7.16373 9.89497 1.872<br>C 7.16203 4.94814 1.8954<br>C 7.87619 6.17677 1.8996<br>C 5.73634 12.3522 1.8872<br>C 0.772689 3.69102 1.898<br>
C 0.762793 1.22003 1.8968<br>C 7.87645 11.1337 1.8894<br>C 7.16203 12.3587 1.889<br>C 7.87201 13.5922 1.8942<br>C 2.89479 2.46619 1.8922<br>
C 1.47482 2.45878 1.8952<br>Ti 6.41604 8.65974 3.74<br>K_POINTS {automatic} <br>6.0 6.0 1.0 1.0 1.0 1.0<br><br>Can anyone help me understanding how are these Cell parameters calculated?<br>
Also in some cases celld(m) are used. Can anyone comment on these also?<br>How are the cell parameters and lattice constant or atomic spacing related?<br><br>Any clue would be of great help.<br><br>Thanks in advance.<br>
<br>
Rgds<br>Deepak<br></pre><br>
<br>_______________________________________________<br>
Pw_forum mailing list<br>
<a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>
<a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>
<br></blockquote></div><br><br clear="all"><br>-- <br>Regards,<br>MOHNISH,<br>-----------------------------------------------------------------<br>Mohnish Pandey<br>Senior Project Associate,<br>Department of Chemical Engineering,<br>
IIT KANPUR, UP, INDIA<br>-----------------------------------------------------------------<br>