Dear Shaptrishi Sharma,<br> I am also a student like you and what i have understood, what is K points, is as follows.<br><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CUsers%5Cravi%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CUsers%5Cravi%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" href="file:///C:%5CUsers%5Cravi%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_colorschememapping.xml"><style>
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</p><p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">We know that charge density is given by</span></p>
<p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">ῤ(r) = <span style=""> </span>Σ<sub>i=1</sub>
<sup>Ne/2</sup> |Ψ<sub>i</sub>(r)|<sup>2</sup></span></p>
<p class="MsoNormal"><sup><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";"><span style=""> </span>with
the Bloch theorem we can write as</span></sup></p>
<p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">ῤ= Σ<sub>n=1</sub> <sup>Ne/cell</sup> ʃ d<sup>3</sup>k|Ψ<sub>kn</sub>(r)|<sup>2</sup></span></p>
<p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";"><span style=""> </span>but since the
integration is a continuous quantity, we choose the K point mesh in the
Brillouin Zone <span style=""> </span>and we have</span></p>
<p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">ῤ= Σ<sub>n=1</sub> <sup>Nb</sup> (2Π)<sup>3</sup>/V Σ
<sub>(k ε mesh in BZ)</sub> <span style=""> </span>d<sup>3</sup>k|Ψ<sub>kn</sub>(r)|<sup>2</sup></span></p>
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</p><p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">Where <span style=""> </span>Ψ<sub>kn</sub>(r)=
e<sup>ik.r</sup> Σ<sub>(G=reciprocal Lattice vector) </sub>C<sub>kn</sub>[e<sup>iG.r</sup>/V<sup>(1/2)</sup>]</span></p>
<span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";"><span style=""> </span>And the term in bracket is the plane wave
basis </span><p></p><p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">and for visualization, what u can do, make any
structure, open with Xcrysden ,and go to tools</span><span style="font-size: 20pt; line-height: 115%; font-family: Wingdings;"><span style=""> --></span></span><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";"> K-path
selection, there the BZ of your structure will be displayed, with some high
symmetry K points (dots).</span></p><p class="MsoNormal"><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CUsers%5Cravi%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CUsers%5Cravi%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" href="file:///C:%5CUsers%5Cravi%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_colorschememapping.xml"><style>
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</p><p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">Dear Shaptrishi Sharma, also a lot of times they
have asked you to provide your full affilation. Please Do it.</span></p>
<br><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";"></span><p></p>
<span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">To all my guides, in the
forum, I may be wrong at any point above, if so please correct me as my group is
totally experimental and its my own understanding.</span><p></p><p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">Dev Sharma, <br></span></p>
<p class="MsoNormal"><span style="font-size: 20pt; line-height: 115%; font-family: "Times New Roman","serif";">University of Delhi<br></span></p>
<br><br><div class="gmail_quote">On Fri, Sep 11, 2009 at 5:29 PM, Stefano de Gironcoli <span dir="ltr"><<a href="mailto:degironc@sissa.it">degironc@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 class="im">Shaptrishi Sharma wrote:<br>
> Hi QEs users,<br>
><br>
> Can anybody please help me in understanding what are the k points ?? I<br>
> have read books a lot but its difficult to understand.<br>
</div>Please ask to any solid state physicist nearby.<br>
<div class="im"><br>
> And also how do we choose k points while performing a band structure<br>
> calculation in quantum espresso when we are having 330 atoms.<br>
</div>If you still have QE specific doubts after you have understood Bloch<br>
theorem, Real and Reciprocal Space lattices, Brilloun Zone and the like<br>
please formulate them again, trying to be specific.<br>
> Thanks<br>
> S<br>
Please provide your affilaition.<br>
<br>
Best regards,<br>
<br>
Stefano de Gironcoli - SISSA and DEMOCRITOS<br>
<br>
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