<div dir="ltr"><div class="gmail_default" style="font-family:'arial black',sans-serif"><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, May 12, 2014 at 9:20 AM, Caroline <span dir="ltr"><<a href="mailto:katesedate@gmail.com" target="_blank">katesedate@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><div><div><div>Dear all, <br><br></div>
I am trying to understand the significance of k points in the input file. Can you please help me with the following questions:<br><br></div>1) How k points are selected? Dos it have to with the dimension of the crystal? Say for 2 dimension crystal only two lines in K point section is defined?<br>
<br></div>2) Or k points have to do with the numerical solution of integrals? I am confused how to define these values, and how they are important. <br><br></div><div>3) Is there a relation between number of k points and number of atoms in the lattice crystal?<br>
</div><div><br><br></div><div>I have read text books on this, and learned that k points need to selected in such a way that total energy is converged.<br></div></div></blockquote><div><br></div><div><div class="gmail_default" style="font-family:'arial black',sans-serif">
you obviously have either not read enough, or need to discuss with somebody local to clear up some fundamental issues. explaining them (thoroughly) in an e-mail would simply result in another textbook-like text.</div><div class="gmail_default" style="font-family:'arial black',sans-serif">
<br></div><div class="gmail_default" style="font-family:'arial black',sans-serif">as a starting point, the k-points result automatically from the reformulation of the schroedinger equation for periodic systems and the resulting condition that the solution has to be commensurate with the periodicity of the system, i.e. it has to be bounded by the simulation box or be periodic over one or more primitive cells in each direction.</div>
<div class="gmail_default" style="font-family:'arial black',sans-serif"><br></div><div class="gmail_default" style="font-family:'arial black',sans-serif">a second simple relation to keep in mind is, that a solution where you double the system in one direction, is equivalent to a calculation where you keep the system but sample over two evenly spaces k-points in that same direction. </div>
<br></div><div><div class="gmail_default" style="font-family:'arial black',sans-serif">i think with these rather general descriptions, you should re-read your textbook(s) (and perhaps try a different one, e.g. this one which i find particularly suited for somebody at your level of understanding: <a href="http://www.amazon.com/Electronic-Structure-Calculations-Solids-Molecules/dp/0521815916">http://www.amazon.com/Electronic-Structure-Calculations-Solids-Molecules/dp/0521815916</a></div>
<div class="gmail_default" style="font-family:'arial black',sans-serif">) and then discuss with your colleagues, adviser, professor etc. a mailing list is a bad replacement for these kind of discussions and they are essential for a proper insight into the methods)</div>
<div class="gmail_default" style="font-family:'arial black',sans-serif"><br></div><div class="gmail_default" style="font-family:'arial black',sans-serif"><br></div><div class="gmail_default" style="font-family:'arial black',sans-serif">
axel.</div><div class="gmail_default" style="font-family:'arial black',sans-serif"></div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div dir="ltr"><div><br></div><div>Please help me with this.<br></div><div>Thanks a lot,<br>
</div><div>C.<br></div><div><div><div><br></div></div></div></div>
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College of Science & Technology, Temple University, Philadelphia PA, USA<br>International Centre for Theoretical Physics, Trieste. Italy.
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