Hi <span class="gD" style="color: rgb(0, 104, 28);">Ashish Kumar, if you don't know: vc-relax means variable-cell relax</span><a name="id3775075"></a><a name="calculation">. So, you're doing this kind of calculation, where the default is relax all cell parameters ( axis, angles, position). You can choose which parameters are fixed or which parameters are relaxed, please read the QE manual, the section &CELL , the variable "cell_dofree"<br>
<br></a>Best.<br><br>PhD stud Arles V. Gil Rebaza<br>IFLP - Argentina<br><br><div class="gmail_quote">2011/10/4 Ashish Kumar <span dir="ltr"><<a href="mailto:ashishespresso@gmail.com">ashishespresso@gmail.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Hello to all,<br><br>I have tried for the vc-relax of Mo2C hexagonal
system, job is not done properly it come out in between and the atomic
positions <br><br>what I have given in the input file and what I am getting in the out file is different. <br>
(i) Why the crystal positions changes. what I think that the nature of the atomic postions must be retained.<br><br>In Input file<br>ATOMIC_POSITIONS (alat)<br>
C 0.00 0.00 0.00<br>
Mo 0.3333333 0.666666 0.25<br>
Mo 0.6666666 0.333333 0.75<br>
<br><br><br>In out file we get<br><br>CELL_PARAMETERS (alat= 5.67296009)<br> 0.946518633 0.001215132 -0.004855406<br> -0.474470641 0.819090796 -0.000958606<br> 0.009278926 0.007480907 1.741942673<br><br>ATOMIC_POSITIONS (alat)<br>
C 0.156590059 0.041446237 -0.212516996<br>Mo 0.157761886 0.589915381 0.269109338<br>Mo 0.636664528 0.321113609 1.041609035<br><br><br><br><br>(ii) why cell_parameter changes in the out file . (I think that for hexagonal system it must be what given in the input file)<br>
<br><br>my input file<br><br>&control<br> calculation='vc-relax'<br> restart_mode='from_scratch',<br> pseudo_dir = '/home/ashish/softwares/espresso/pseudo/',<br> outdir='/home/ashish/dft/espresso_mo2c/test1/tmp_espresso/'<br>
prefix='mo2c'<br> tprnfor = .true.,<br> tstress = .true.<br> /<br> &system<br> ibrav=4, celldm(1) =5.672960087 , celldm(3)=1.573617588 , nat=3, ntyp=2,<br> nspin = 1, starting_magnetization(1)=0.7,<br>
ecutwfc = 24.0, ecutrho = 288.0, <br> occupations='smearing', smearing='methfessel-paxton', degauss=0.02<br> /<br> &electrons<br> diagonalization='cg'<br> conv_thr = 1.0e-8<br> mixing_beta = 0.7<br>
/<br>&ions<br> ion_dynamics='bfgs'<br> /<br>&cell<br>cell_dynamics='bfgs'<br>/<br>ATOMIC_SPECIES {crystal}<br> C 12.01 C.pw91-van_ak.UPF <br> Mo 95.94 Mo.pw91-n-van.UPF <br>ATOMIC_POSITIONS<br>
C 0.0 0.0 0.0<br>
Mo 1/3 2/3 1/4<br> Mo 2/3 1/3 3/4<br><br>K_POINTS automatic<br> 4 4 4 0 0 0 <br><br><br> can any one help me. What is the mistake (in my input file or else)<br><br><br>with best wishes<br><font color="#888888"><font color="#888888">Ashish<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>###---------> Arles V. <---------###<br>