<p dir="ltr">There is nothing wrong so long as this is only a few percent although this is a bit unusual. Normally PBE gives lattice constants too large, LDA too small with PBEsol & WC closer to experiment. I myself do not consider agreement between expt & calculated lattice constants (within a few percent) to be a very useful test of functionals despite what is in the literature.</p>
<p dir="ltr">______________________________<br>
Laurence Marks<br>
Dept Mat Sci & Eng<br>
Northwestern University<br>
<a href="http://www.numis.northwestern.edu">www.numis.northwestern.edu</a><br>
847 491 3996</p>
<div class="gmail_quote">On Jan 30, 2014 8:13 AM, "kalsoom Khan" <<a href="mailto:kkkhan.queen@yahoo.com">kkkhan.queen@yahoo.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div style="font-size:12pt;font-family:HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif">
<div>Dear all</div>
<div>I have problem in optimization, i want to optimize the the lattice constant.. but i have contrast in the reults. I did the optimization for two cubic compounds, in which for one compound the lattice constant increased from the experimental values. While
for the other compound the lattice constant were decreased.</div>
<div>so please help me that which one is wrong. Either the optimized lattice constant increased or decreased.</div>
<div>with regards</div>
<div>kalsoom</div>
</div>
</div>
</blockquote></div>