[Pw_forum] GGA+U

[ali kazempour]

Dear all

>From Linear response calculation ,I get for TiO2 bulk U=5.73, But when I double the unit cell in z direction and again compute U ,I get three different value for Ti atoms.(U=5.63,5.46,5.70).
Why these values are not same . what is the main reason? Does it in numerical variation errors?
ANother question:
When we perturb D level by alpha, it give rise to change in d occupancy . Is it correct that if we impose negative alpha , the occupation becomes less than initial state .?
for Ti isolated atom for apha=0.1  tr[ns(na)] after first-iteration equal to the 0.002 and at the end of calculation is 2.327 while we know that for Ti,  tr[ns(na)] =2.000. Does it seems to be correct.?

     Number of iteration with fixed ns =  0
     Starting ns and Hubbard U :
 enter write_ns
U( 1) =  0.0000
alpha( 1) =  0.1000
atom  1   Tr[ns(na)]=   2.0000000
atom  1  spin  1
eigenvalues:  0.4000000 0.4000000 0.4000000 0.4000000 0.4000000
 eigenvectors
 1   1.0000000  0.0000000  0.0000000  0.0000000  0.0000000
 2   0.0000000  1.0000000  0.0000000  0.0000000  0.0000000
 3   0.0000000  0.0000000  1.0000000  0.0000000  0.0000000
 4   0.0000000  0.0000000  0.0000000  1.0000000  0.0000000
 5   0.0000000  0.0000000  0.0000000  0.0000000  1.0000000
 occupations
 0.400  0.000  0.000  0.000  0.000
 0.000  0.400  0.000  0.000  0.000
 0.000  0.000  0.400  0.000  0.000
 0.000  0.000  0.000  0.400  0.000
 0.000  0.000  0.000  0.000  0.400
atom  1  spin  2
eigenvalues:  0.0000000 0.0000000 0.0000000 0.0000000 0.0000000
 eigenvectors
 1   1.0000000  0.0000000  0.0000000  0.0000000  0.0000000
 2   0.0000000  1.0000000  0.0000000  0.0000000  0.0000000
 3   0.0000000  0.0000000  1.0000000  0.0000000  0.0000000
 4   0.0000000  0.0000000  0.0000000  1.0000000  0.0000000
 5   0.0000000  0.0000000  0.0000000  0.0000000  1.0000000
 occupations
 0.000  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.000  0.000
nsum =   2.0000000
 exit write_ns
 Atomic wfc used for LDA+U Projector are NOT orthogonalized
     Starting wfc are    9 atomic +    1 random wfc

     total cpu time spent up to now is     13.34 secs

     per-process dynamical memory:   326.3 Mb

     Self-consistent Calculation

     iteration #  1     ecut=    45.00 Ry     beta=0.70
     CG style diagonalization
     c_bands:  3 eigenvalues not converged
     c_bands:  2 eigenvalues not converged
     ethr =  1.00E-12,  avg # of iterations = 40.4
 enter write_ns
U( 1) =  0.0000
alpha( 1) =  0.1000
atom  1   Tr[ns(na)]=   0.0021401
atom  1  spin  1
eigenvalues:  0.0000001 0.0000001 0.0000001 0.0009883 0.0009883
 eigenvectors
 1   0.0000000 -0.8803392 -0.4743427  0.0000000  0.0013927
 2   0.0000000 -0.4743432  0.8803400  0.0000000 -0.0000040
 3   0.0000000  0.0012242  0.0006642  0.0000000  0.9999990
 4  -0.8886820  0.0000000  0.0000000 -0.4585240  0.0000000
 5   0.4585240  0.0000000  0.0000000 -0.8886820  0.0000000
 occupations
 0.001  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.000  0.000
 0.000  0.000  0.000  0.001  0.000
 0.000  0.000  0.000  0.000  0.000
---------------------------------- and end of the file is 
:
     End of self-consistent calculation
 enter write_ns
U( 1) =  0.0000
alpha( 1) =  0.1000
atom  1   Tr[ns(na)]=   2.3270531
atom  1  spin  1
eigenvalues:  0.1574294 0.1574294 0.1574294 0.9273825 0.9273825
 eigenvectors
 1   0.0000000 -0.4359030 -0.7986559  0.0000000  0.4148945
 2   0.0000000  0.7269732 -0.0406891  0.0000000  0.6854592
 3   0.0000000 -0.5305643  0.6004109  0.0000000  0.5983379
 4  -0.9258933  0.0000000  0.0000000 -0.3777851  0.0000000
 5   0.3777851  0.0000000  0.0000000 -0.9258933  0.0000000
 occupations
 0.927  0.000  0.000  0.000  0.000
 0.000  0.157  0.000  0.000  0.000
 0.000  0.000  0.157  0.000  0.000
 0.000  0.000  0.000  0.927  0.000
 0.000  0.000  0.000  0.000  0.157


Thanks a lot
Ali Kazempour

Physics department, Isfahan University of Technology

84156 Isfahan, Iran.            Tel-1:  +98 311 391 3733

Fax: +98 311 391 2376      Tel-2:  +98 311 391 2375


      
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