<br>Hi, <br>A comment: <br>Spin polarization calculation should be applied for the isolated atom.<br><br>Hope it helps, and please supply your affiliation<br><br>regards<br><div class="gmail_quote">On Tue, Sep 1, 2009 at 2:18 AM, udayagiri sai babu <span dir="ltr"><<a href="mailto:udayagiri3@gmail.com">udayagiri3@gmail.com</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;">Hi all<br>i am claculating cohesive energy of V using pwscf but i got -8.15 ev/atom against an experimental value of 5.3 ev/atom which is almost 50% off can anybody say what is going wrong with the calculation. the method i used is calculate the total energy of a bcc crystal with 1 atom and deduct the energy of isolated atom from it. the following input files are for finding the total energy for isolated atom and the atom in the crystal. Please tell me if my methodology is wrong.<br>
<br><b>cohesive energy=E per atom (in the crystal)-E per atom (isolated)</b><br><br><b>input file for finding the total energy of an isolated atom</b><br><br>&control<br>calculation = 'scf',<br>restart_mode='from_scratch',<br>
outdir='/home/sai/temp',<br>prefix='vanadium'<br>pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',<br>tstress = .TRUE.,<br>tprnfor = .TRUE.,<br>/<br>&system<br>ibrav=1<br>celldm(1)=30,<br>
nat=1,<br>ntyp=1<br>ecutwfc=25,<br>ecutrho=100,<br>occupations='smearing',<br>smearing='mv',<br>degauss=0.010000<br>/<br>&electrons<br>conv_thr=1.D-8,<br>diagonalization='david',<br> mixing_mode='plain',<br>
mixing_beta= 0.3<br>/<br>ATOMIC_SPECIES<br>V 50.9415 V.pbe-n-van.UPF<br>ATOMIC_POSITIONS (crystal)<br>V 0.00000000 0.00000000 0.00000000<br>K_POINTS {automatic}<br>1 1 1 0 0 0<br><br><b>input file for finding the total energy of the atom in the crystal</b><br>
<br>&control<br>calculation = 'scf',<br>restart_mode='from_scratch',<br>outdir='/home/sai/temp',<br>prefix='vanadium'<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)=5.654,<br>nat=1,<br>ntyp=1<br>ecutwfc=25,<br>ecutrho=100,<br>occupations='smearing',<br>smearing='mv',<br>degauss=0.010000<br>
/<br>&electrons<br>conv_thr=1.D-8,<br>diagonalization='david',<br>mixing_mode='plain',<br>mixing_beta= 0.3<br>/<br>ATOMIC_SPECIES<br>V 50.9415 V.pbe-n-van.UPF<br>ATOMIC_POSITIONS (crystal)<br>V 0.00000000 0.00000000 0.00000000<br>
K_POINTS {automatic}<br>8 8 8 0 0 0<br><br><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Hai-Ping Lan <br>Department of Electronics ,<br>Peking University , Bejing, 100871<br><a href="mailto:lanhaiping@gmail.com">lanhaiping@gmail.com</a>, <a href="mailto:hplan@pku.edu.cn">hplan@pku.edu.cn</a><br>