Dear stefano baroni<br>I tried that as well i am getting the same value (255gpa). This is the data i am using<br><br>5.35 -174.156857800<br>5.36 -174.156934850<br>5.37 -174.156989300<br>5.38 -174.156990580<br>5.39 -174.156955990<br>
5.4 -174.156869280<br><br>this is one of the input file <br><br> &control<br>calculation = 'scf',<br>restart_mode='from_scratch',<br>outdir='/home/sai/temp',<br>prefix='chromium'<br>
pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',<br>tstress = .TRUE.,<br>tprnfor = .TRUE.,<br>/<br>&system<br>ibrav=3<br>celldm(1)=5.350000,<br>nat=1,<br>ntyp=1<br>ecutwfc=30,<br>ecutrho=300,<br>occupations='smearing',<br>
smearing='mv',<br>degauss=0.012000<br>/<br>&electrons<br>conv_thr=1.D-8,<br>diagonalization='david',<br>mixing_mode='plain',<br>mixing_beta= 0.7<br>/<br>ATOMIC_SPECIES<br>Cr 51.9961 Cr.pw91-sp-van.UPF<br>
ATOMIC_POSITIONS (crystal)<br>Cr 0.00000000 0.00000000 0.00000000<br>K_POINTS {automatic}<br>12 12 12 0 0 0<br><br>can you suggest me anything <br><br><div class="gmail_quote">On Wed, Sep 9, 2009 at 1:03 AM, Stefano Baroni <span dir="ltr"><<a href="mailto:baroni@sissa.it">baroni@sissa.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div style="">How about trying to fit a very accurate set of data around the minimum with a parabola and calculate thus the bulk modulus? Have you tries to plot the resulting fitted curves? which one fits best the raw data? Udaygiri: in Science (as well as in Life) there is no free lunch ... Enjoy Science, no less than Life. SB<div>
<br><div><div><div></div><div class="h5"><div>On Sep 8, 2009, at 9:04 PM, udayagiri sai babu wrote:</div><br></div></div><blockquote type="cite"><div><div></div><div class="h5"><br clear="all">hi all<br>i am using ev.x file given in the pw_tools directory to calculate bulk modulus and lattice parameter values of chromium. i used murnaghan equation of state to fit my data i got bulk modulus of 256 gpa where as my experimental value is 160 gpa but when i used keane equation of state to fit the same data i got 148 gpa bulk modulus <br>
<br>why is this much variation? which equation of state should i use for cr? because for vanadium and Ti murnagan euation of state has given reasonable (<20% error) values of bulk modulus but not for Cr<br><br>please give some suggestions<br>
-- <br>U.Saibabu<br>PhD student,<br>Deformation mechanisms modeling group,<br>Materials engineering department,<br>IISc Bangalore,<br>India.<br><br></div></div> _______________________________________________<br>Pw_forum mailing list<br>
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<div style="margin: 0px;"><font size="3"><span style="font-size: 12px;"><br></span></font></div></span></div><div style="margin: 0px;"><font size="3"><span style="font-size: 12px;">Please, if possible, don't</span></font><font size="3"><span style="font-size: 12px;"> </span></font><font size="3"><span style="font-size: 12px;">send me MS Word or PowerPoint attachments</span></font></div>
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<br></blockquote></div><br><br clear="all"><br>-- <br>U.Saibabu<br>PhD student,<br>Deformation mechanisms modeling group,<br>Materials engineering department,<br>IISc Bangalore,<br>India.<br><br>