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<div dir="ltr" data-setdir="false">Dear Mr. <span><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Kondrin,</span></span></div><div dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br></span></span></div><div dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Thanks, this is exactly for silicon. </span></span></div><div dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br></span></span></div><div dir="ltr" data-setdir="false"><span><div><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Best</span><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> Regards,</span></div><div><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br></span></div><div><span style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">HY Lu</span></div></span></div><div><br></div>
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在 2023年11月12日 星期日 下午02:52:03 [GMT+8]， <mkondrin@hppi.troitsk.ru> 寫道：
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<div><div dir="ltr">Hi, Ludwig<br clear="none"><br clear="none">Raman modes should be calculate in primitive unit cell so you get the <br clear="none">correct number of phonon modes. In silicon you get six modes -- triply <br clear="none">degenerate Raman mode and three acoustic modes.<br clear="none"><br clear="none">Sincerely yours,<br clear="none">M.V.Kondrin<br clear="none"> <div class="ydpbcaff425yqt6504658270" id="ydpbcaff425yqtfd52572"><br clear="none">On Nov 12 2023, <a shape="rect" href="mailto:ludwigboltzmann.sc10@nycu.edu.tw" rel="nofollow" target="_blank">ludwigboltzmann.sc10@nycu.edu.tw</a> wrote:<br clear="none"><br clear="none">> Dear users: I am going to calculate Raman spectra for organic perovskite. <br clear="none">> (only at Gamma point)My flow chart is like this： pw.x vc-relax(geometry <br clear="none">> optimization)→pw.x scf→ph.x→dynmat.xIn Phonon Calculation for Raman <br clear="none">> Spectra , How to decide to use how many unit cells?<br clear="none">><br clear="none">> I saw what in the tutorial, for silicon in primitive cell, Si only has 2 <br clear="none">> atoms in a primitive cell, and the tutorial used 2 atoms (1 unit cell to <br clear="none">> calculate)Ref:https://www.quantum-espresso.org/wp-content/uploads/2022/03/phonons_tutorial_shanghai1.pdf<br clear="none">><br clear="none">><br clear="none">> However, according to the paper I read, the author used 4 unit cells to <br clear="none">> calculate, is this going to make some difference? Is it ok to <br clear="none">> calculate Raman spectra with on one unit cell?Difference I could imagine <br clear="none">> is that if I had 1unit cell with 24 atoms,With 1 unit cell (24 atoms), I <br clear="none">> can get 72(3*24) modes at Gamma point. With 2 unit cell (48 atoms), I can <br clear="none">> get 144(3*48) modes at Gamma point. With 4 unit cell (96 atoms), I can <br clear="none">> get 288(3*96) modes at Gamma point. As the unit cell increased, I would <br clear="none">> get more modes at Gamma point.However, it takes more time to do the <br clear="none">> calculation.I'm wondering what's the difference to do phonon calculation <br clear="none">> to use different number of unit cells? And how to decide it? Best <br clear="none">> Regards,HY Lu<br clear="none"><br clear="none"></div></div></div>
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