[Pw_forum] bandgap of germanium

[华 李]

Dr. B. Bouhafs:
 
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.
 
Sincerely your,
 
tylv
Bachir Bouhafs <bbouhafs at mail.com> wrote:

Dear  User,

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.  

Sincerely your,

Dr. B. Bouhafs

----- Original Message -----
From: 华 李 
Date: Fri, 30 Jul 2004 20:21:47 +0800 (CST)
To: pw_forum at pwscf.org
Subject: [Pw_forum] bandgap of germanium


dear all:
          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?
*************************************************************************************
I adjust input file of Si to the one of Ge 
celldm(1)=  10.6769
ATOMIC_SPECIES
 Ge  72.59   Ge.pz-bhs.UPF
ATOMIC_POSITIONS
 Ge 0.00 0.00 0.00
 Ge 0.25 0.25 0.25
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
I get the bands :
         k = 0.0000 0.0000 0.0000 (  387 PWs)   bands (ev):
    -6.8856   5.7367   5.7367   5.7367   6.3235   8.2033   8.2033   8.2033
          k = 0.1000 0.1000 0.1000 (  381 PWs)   bands (ev):
    -6.7709   3.9714   5.5040   5.5040   7.0825   8.5187   8.5187   8.9337
          k = 0.2000 0.2000 0.2000 (  386 PWs)   bands (ev):
    -6.4324   1.9466   5.0670   5.0670   6.7871   9.0770   9.0770  10.7253
          k = 0.3000 0.3000 0.3000 (  395 PWs)   bands (ev):
    -5.8950   0.1370   4.6838   4.6838   6.3897   9.3538   9.3538  12.4674
          k = 0.4000 0.4000 0.4000 (  389 PWs)   bands (ev):
    -5.2555  -1.2853   4.4397   4.4397   6.1241   9.3304   9.3304  12.8071
          k = 0.5000 0.5000 0.5000 (  392 PWs)   bands (ev):
    -4.8902  -1.9150   4.3561   4.3561   6.0326   9.2850   9.2850  12.6981





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Dr. Bachir BouhafsPhysics DepartmentUniversity of Sidi Bel Abbes22000 Sidi Bel Abbes, AlgeriaMobil:+213 (0)71 18 21 47Fax:+213 48 54 11 52 E-mail: bbouhafs at mail.com

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