<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt">Dear Giuseppe,<br><br>Thank you for your answer. It is very helpful for me. I will use your advice in my calculation. :-)<br><br>Regards,<br>Angga<br><div><span><br></span></div><div> </div><div><span style="font-weight:bold;font-family:arial, helvetica, sans-serif;">Angga Dito Fauzi</span></div><div><span style="font-family:arial, helvetica, sans-serif;">Undergraduate Student</span></div><div><span style="font-family:arial, helvetica, sans-serif;">Department of Physics, Faculty of Mathematics and Natural Sciences</span></div><div><span style="font-family:arial, helvetica, sans-serif;">Universitas Indonesia, Depok 16424, Indonesia</span></div><div><span style="font-family:arial, helvetica, sans-serif;">Phone: +628124139348</span></div><div><span style="font-family:arial, helvetica, sans-serif;">Email:
angga_dito_fauzi@yahoo.com</span></div><div><br></div> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font face="Arial" size="2"> <hr size="1"> <b><span style="font-weight:bold;">Dari:</span></b> Giuseppe Mattioli <giuseppe.mattioli@ism.cnr.it><br> <b><span style="font-weight: bold;">Kepada:</span></b> Angga Fauzi <angga_dito_fauzi@yahoo.com>; PWSCF Forum <pw_forum@pwscf.org> <br> <b><span style="font-weight: bold;">Dikirim:</span></b> Kamis, 10 Januari 2013 18:54<br> <b><span style="font-weight: bold;">Judul:</span></b> Re: [Pw_forum] Bls: Relax Calculation for ZnO<br> </font> </div> <br><br>Dear Angga<br>A 32 atoms ZnO cells is not so big. I recommend you to perform a bunch of different calculations in <br>order to touch with your hands the difference between fixed occupations, smearing
methods, ...<br>But let us say that in the case of a ZnO bulk you should not find differences between fixed and <br>smearing (start always with Gaussian smearing: it improves the scf convergence) calculations because <br>an intrinsic semiconductor is in fact an insulator: No electron (or significant fraction of electron) <br>will cross the band gap and populate the conduction band, even if the GGA ZnO gap is generally <br>reduced to the quite low value of about 1.0 eV. You can check it by the smearing contribution to the <br>total energy, which will be negligible. When you dope the ZnO lattice with a TM atom (a 32 atoms <br>cell is too small: the TM atom will strongly interact with its periodically repeated image) the <br>system could turn out to be a semiconductor, that is, technically speaking, a "metal" with the Fermi <br>energy crossing some bands. Here you must use smearing, or you will never reach the scf convergence. <br>I always use a low
Gaussian smearing (0.01 Ry) to relax this kind of system. After relaxing the <br>system, you can try to restart from the final positions by using different smearing values and kinds <br>(mv, fd, ...) and check if the results are the same (usually they are!). You do not need to perform <br>a scf calculation after the relax one to calculate the band structure, unless you are performing EXX <br>calculations which do not allow for the nscf procedure. In the case of vc-relax calculations, the <br>code itself performs a final, unbiased, scf calculation because of the change of the k-points mesh <br>along the vc-relax procedure, but this is not necessary in the case of simple relax calculations.<br><br>HTH<br><br>Giuseppe<br><br><br>On Thursday 10 January 2013 12:16:59 Angga Fauzi wrote:<br>> Dear Nazari,<br>> <br>> Thank you for your answer. I want to ask again.<br>> <br>> 1. According to your answer for my first question,
since my system is ZnO,<br>> which is a semiconductor, then I use occupations = 'fixed'. How if my<br>> system is TM-doped ZnO? Should I use occupations = 'fixed' again or I<br>> replace it with occupations = 'smearing'? 2. According to your answer for<br>> my second question, is it means that after my relax calculation is done, I<br>> can directly run nscf calculation to calculate band structure or I have to<br>> run scf calculation first and then nscf calculation? Regards,<br>> Angga<br>> <br>> Angga Dito Fauzi<br>> Undergraduate Student<br>> Department of Physics, Faculty of Mathematics and Natural Sciences<br>> Universitas Indonesia, Depok 16424, Indonesia<br>> Phone: +628124139348<br>> Email: <a ymailto="mailto:angga_dito_fauzi@yahoo.com" href="mailto:angga_dito_fauzi@yahoo.com">angga_dito_fauzi@yahoo.com</a><br>> <br>> <br>> ________________________________<br>> Dari: "<a
ymailto="mailto:nazari@iasbs.ac.ir" href="mailto:nazari@iasbs.ac.ir">nazari@iasbs.ac.ir</a>" <<a ymailto="mailto:nazari@iasbs.ac.ir" href="mailto:nazari@iasbs.ac.ir">nazari@iasbs.ac.ir</a>><br>> Kepada: Angga Fauzi <<a ymailto="mailto:angga_dito_fauzi@yahoo.com" href="mailto:angga_dito_fauzi@yahoo.com">angga_dito_fauzi@yahoo.com</a>>; PWSCF Forum<br>> <<a ymailto="mailto:pw_forum@pwscf.org" href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</a>> Dikirim: Kamis, 10 Januari 2013 15:18<br>> Judul: Re: [Pw_forum] Relax Calculation for ZnO<br>> <br>> > Dear all QE users,<br>> > <br>> > I am trying to run relax<br>> <br>> calculation for my ZnO system. There are<br>> <br>> > something I want to<br>> <br>> ask.<br>> <br>> > 1. In running relax calculation, what occupations should I<br>> <br>> use? I am<br>> <br>> > trying to use occupations = 'tetrahedra', but
it<br>> <br>> doesn't work. I am<br>> <br>> > afraid if I use occupations = 'smearing', my<br>> <br>> result calculation doesn't<br>> <br>> > valid since ZnO is a semiconductor,<br>> <br>> not a metal. <br>> <br>> For semiconductor <br>> occupations=fixed<br>> <br>> > 2. After my relax calculation is<br>> <br>> done, should I run a scf calculation<br>> <br>> > again with atomic<br>> <br>> positions I get from relax calculation? <br>> <br>> For what?<br>> <br>> <br>> > I also attach my<br>> <br>> input file. Thank you very much for your attention.<br>> <br>> <br>> Regards,<br>> <br>> > Angga<br>> > <br>> > Angga Dito Fauzi<br>> > Undergraduate Student<br>> > Department of Physics, Faculty<br>> <br>> of Mathematics and Natural Sciences<br>> <br>> >
Universitas Indonesia,<br>> <br>> Depok 16424, Indonesia<br>> <br>> > Phone: +628124139348<br>> <br>> > Email:<br>> <a ymailto="mailto:angga_dito_fauzi@yahoo.com" href="mailto:angga_dito_fauzi@yahoo.com">angga_dito_fauzi@yahoo.com</a><br>> scanned for viruses and<br>> <br>> > dangerous content by MailScanner, and<br>> <br>> is<br>> <br>> > believed to be clean.<br>> <br>> _______________________________________________<br>> <br>> > Pw_forum<br>> <br>> mailing list<br>> <br>> > <a ymailto="mailto:Pw_forum@pwscf.org" href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>> <br>> <a href="http://pwscf.org/mailman/listinfo/pw_forum" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a><br><br>-- <br>********************************************************<br>- Article premier - Les hommes naissent et demeurent<br>libres et ègaux en droits. Les
distinctions sociales<br>ne peuvent être fondèes que sur l'utilitè commune<br>- Article 2 - Le but de toute association politique<br>est la conservation des droits naturels et <br>imprescriptibles de l'homme. Ces droits sont la libertè,<br>la propriètè, la sùretè et la rèsistance à l'oppression.<br>********************************************************<br><br> Giuseppe Mattioli <br> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA <br> v. Salaria Km 29,300 - C.P. 10 <br> I 00015 - Monterotondo Stazione (RM) <br> Tel + 39 06 90672836 - Fax +39 06 90672316 <br> E-mail: <<a ymailto="mailto:giuseppe.mattioli@ism.cnr.it"
href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>><br><br><br> </div> </div> </div></body></html>