<P><FONT face=Arial size=2>Dear User,</FONT></P>
<P><FONT face=Arial size=2>I have made a mistake when I've calculated the band-gap, As you say, the calculated value is 0.2959 eV, which is positive. So, in this situation, I think that you have calculated your band structure at the experimental lattice parameter (see 5,64989 <FONT color=#1f1a17><STRONG>(A) </STRONG></FONT><FONT color=#000000>your value compared with the</FONT><FONT color=red><STRONG> </STRONG>experimental l<STRONG>attice constant </STRONG><FONT color=#000000> </FONT><FONT color=red>5.64613 <STRONG>(A) </STRONG></FONT><STRONG>at 300 K</STRONG></FONT> ) which is greater that the LDA value. Which means, that you have applied a negative pressure to your crystal, and consequently the band gap increases. I don't know, if you have used your optimized lattice constant, which can be obtained using PWSCF code by minimizing the total energy. When you use your LDA lattice constant, which is smaller than the one used here, your band-ga
p will decreases, and will be negative.</FONT></P>
<P><FONT face=Arial size=2>Best wishes.</FONT></P>
<P><FONT face=Arial size=2>Bachir Bouhafs<BR><BR>----- Original Message -----<BR>From: 华 李 <LVTIEYU1975@YAHOO.COM.CN><BR>Date: Sat, 31 Jul 2004 06:33:29 +0800 (CST)<BR>To: pw_forum@pwscf.org<BR>Subject: Re: [Pw_forum] bandgap of germanium<BR><BR></P></FONT>
<DIV><FONT face=Arial size=2>Dr. B. Bouhafs:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>6.3235 is the value at band number 5! Not at band number 4! So the bandgap is 0.2959 ev, not -0.2909 ev.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Sincerely your,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>tylv<BR><B><I>Bachir Bouhafs <bbouhafs@mail.com></I></B> wrote:</FONT></DIV>
<BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">
<P><FONT face=Arial size=2>Dear User,</FONT></P>
<P><FONT face=Arial size=2>When I take a look at your output data, you find that the calculated band gap is negative and equal to -0,2909 eV. This value is the difference between the first conduction band at L(0.5,0.5,0.5) with the corresponding value of 6.0326 (band number 5) and the top of the valence band at gamma (0.,0.,0.0) with the corresponding value of 6.3235 (band number 4). So, this value obtained by the PWSCF code is acceptable, since the ab-initio band gap using other methods for Ge was found negative using both LDA or GGA. </FONT></P>
<P><FONT face=Arial size=2>Sincerely your,</FONT></P>
<P><FONT face=Arial size=2>Dr. B. Bouhafs<BR><BR>----- Original Message -----<BR>From: 华 李 <LVTIEYU1975@YAHOO.COM.CN><BR>Date: Fri, 30 Jul 2004 20:21:47 +0800 (CST)<BR>To: pw_forum@pwscf.org<BR>Subject: [Pw_forum] bandgap of germanium<BR><BR></FONT></P>
<DIV><FONT face=Arial size=2>dear all:</FONT></DIV>
<DIV><FONT face=Arial size=2> I'm a new user of pwscf code. I successed with calculations for Si in example1. When I tried to calculate Ge, there is a problem. Using other code, we will get nearly 0 ev, even negative. Using pwscf, I get 0.2959 ev. that is ok?</FONT></DIV>
<DIV><FONT face=Arial size=2>*************************************************************************************</FONT></DIV>
<DIV><FONT face=Arial size=2>I adjust input file of Si to the one of Ge </FONT></DIV>
<DIV><FONT face=Arial size=2>celldm(1)= 10.6769</FONT></DIV>
<DIV><FONT face=Arial size=2>ATOMIC_SPECIES<BR> Ge 72.59 Ge.pz-bhs.UPF<BR>ATOMIC_POSITIONS<BR> Ge 0.00 0.00 0.00<BR> Ge 0.25 0.25 0.25</FONT></DIV>
<DIV><FONT face=Arial size=2>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</FONT></DIV>
<DIV><FONT face=Arial size=2>I get the bands :</FONT></DIV>
<DIV><FONT face=Arial size=2> k = 0.0000 0.0000 0.0000 ( 387 PWs) bands (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2> -6.8856 5.7367 5.7367 5.7367 6.3235 8.2033 8.2033 8.2033</FONT></DIV>
<DIV><FONT face=Arial size=2> k = 0.1000 0.1000 0.1000 ( 381 PWs) bands (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2> -6.7709 3.9714 5.5040 5.5040 7.0825 8.5187 8.5187 8.9337</FONT></DIV>
<DIV><FONT face=Arial size=2> k = 0.2000 0.2000 0.2000 ( 386 PWs) bands (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2> -6.4324 1.9466 5.0670 5.0670 6.7871 9.0770 9.0770 10.7253</FONT></DIV>
<DIV><FONT face=Arial size=2> k = 0.3000 0.3000 0.3000 ( 395 PWs) bands (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2> -5.8950 0.1370 4.6838 4.6838 6.3897 9.3538 9.3538 12.4674</FONT></DIV>
<DIV><FONT face=Arial size=2> k = 0.4000 0.4000 0.4000 ( 389 PWs) bands (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2> -5.2555 -1.2853 4.4397 4.4397 6.1241 9.3304 9.3304 12.8071</FONT></DIV>
<DIV><FONT face=Arial size=2> k = 0.5000 0.5000 0.5000 ( 392 PWs) bands (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2> -4.8902 -1.9150 4.3561 4.3561 6.0326 9.2850 9.2850 12.6981<BR><BR></FONT></DIV>
<P><FONT face=Arial><BR><FONT size=2></FONT></FONT></P><FONT face=Arial size=2>
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<B>Do You Yahoo!?</B><BR></FONT><A href="http://image.yisou.com/" target=blank><FONT face=Arial size=2>美女明星应有尽有，"一搜"搜遍美图、艳图和酷图</FONT></A><BR><A href="http://cn.rd.yahoo.com/mail_cn/tag/100m/*http://cn.promo.yahoo.com/minisite/100m/" target=blank><FONT face=Arial size=2>100兆邮箱够不够用？雅虎电邮自助扩容！</FONT></A><FONT face=Arial size=2> <BR><BR></FONT><PRE><FONT face=Arial size=2>Dr. Bachir Bouhafs
Physics Department
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