<div dir="ltr"><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">Dear Users<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">I
have a question regarding the usage of crystal_sg option to specify
atomic position in pw input file. I'm trying make pw i/p file for TiO2
rutile system. its space group # is 136 , Ti is at 2a site and O is at 4e site.so from ITA i have the following i/p data<br><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"><br>Ti 2a (0, 0, 0) (0.5, 0.5, 0.5)<br></div>O 4e (0, 0, z) (0.5, 0.5, z+1/2) (0.5, 0.5, -z+1/2)(0,0,-z)<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">the z value is 0.305. so from this i have created following pw.x input file <br><br>&control<br>    calculation ='scf'<br>    restart_mode = 'from_scratch',<br>          prefix = 'ge'<br>      pseudo_dir = '/home/pearl/qe-5.4.0/pseudo/',<br>        outdir ='/home/pearl/qe-5.4.0/tio2/tmp/'<br> /<br> &system<br>         ibrav = 6 ,<br>    space_group = 136,<br>            A = 4.59373 ,<br>            C = 2.95812 ,<br>          nat = 2 ,   <br>          ntyp = 2 ,<br>       ecutwfc = 20.0 ,<br>       ecutrho = 80.0 ,<br>     occupations = 'smearing' ,<br>         degauss = 0.1 ,<br>        smearing = 'gaussian' ,<br> /<br> &electrons<br>       conv_thr = 1.0d-8 ,<br>    mixing_beta = 0.7 ,<br> /<br>ATOMIC_SPECIES<br> Ti 47.867  Ti.pz-mt_fhi.UPF<br> O  16.000  O.pz-mt_fhi.UPF<br>ATOMIC_POSITIONS crystal_sg<br>Ti  2a <br>O   4e 0.305<br>K_POINTS automatic<br>4 4 4 0 0 0<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">with this file i'm able to run pw.x without any error message. but the following are my questions :<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">1) the atomic position written in output file by pw.x is very different from the expected. why ?<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">from ge.pw.out file i have ( created by pw.x for above input file)<br>Cartesian axes<br>   site n.    atom                 positions (alat units)<br>        1          Ti tau(  1) = (  0.5000000  0.5000000  0.3219736 )<br>        2          Ti tau(  2) = (  0.0000000  0.0000000  0.0000000 )<br>        3          O  tau(  3) = (  0.0000000  0.0000000  0.4475434 )<br>        4          O  tau(  4) = (  0.5000000  0.5000000  0.1255697 )<br>        5          O  tau(  5) = (  0.5000000  0.5000000  0.5183776 )<br>        6          O  tau(  6) = (  0.0000000  0.0000000  0.1964039 )<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">but the atomic positions are (in crystal unit )<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"> Ti   0.000000000        0.000000000        0.000000000<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"> Ti   0.500000000        0.500000000        0.500000000<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"> O  0.305299997        0.305299997        0.000000000<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"> O   0.694700003        0.694700003        0.000000000<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"> O  0.194700003        0.805299997        0.500000000<br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"> O  0.805299997        0.194700003        0.500000000<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">my second question is <br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">2) why QE is not giving correct atomic position if i use crystal_sg option ?<br><br></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)">cay anyone help me in this regard. with this mail i have enclosed the output file for the given input file<br>Thank you <br><br><b><span style="color:rgb(0,0,255)">================================<br></span></b></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif"><b><span style="color:rgb(0,0,255)">Muthu V<br></span></b></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif"><b><span style="color:rgb(0,0,255)">Sri Paramakalyani College<br></span></b></div><div class="gmail_default" style="font-family:comic sans ms,sans-serif;color:rgb(0,0,0)"><b><span style="color:rgb(0,0,255)">Alwarkurichi<br>================================</span></b><br></div></div></div>