<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hem, what a weird request!<div>Why not doing the exercise with pencil-and-paper?</div><div>If you insist using a very sophisticated code to do that, you have two options, I believe, both of which will require somewhat more work than the simple pencil-and-paper exercise.</div><div><ol class="MailOutline"><li>dig into the code where the the hamiltonian*wavefunctions operations are performed (the routine used to be called "h_psi", and simply have the the multiplication times the external potential skipped, which will set the electrons "free" ...</li><li>build a fake pseudo-potential which is simply null, and feed it into the computer ...</li></ol><div><div>HTH - Stefano B</div><div><br></div><div><br></div><div>On Jan 3, 2012, at 6:42 PM, Jun Liu wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Dear All,<br><br>Let me wish all of you a Happy New Year first.<br><br>Maybe this is a very fundamental problem, but I cannot google any hint online, so here I am. I would like to work out a free electron gas problem with QE. I know total number of charges, and the size of the box the electrons move in and probably periodic b.c. applied to it. Now how can I possibly set up the input file for it? It seems many fundamentional properties of a lattice do not come with free electron gas. The code itself should be well-defined for a lattice system, so how is the code adapted to the free electron problem?<br>
<br>Thank you very much,<br> <br>Sincerely,<br>Jun Liu<br><br><br><br>
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