[Pw_forum] Calculation of Raman tensor/intensity for material with indirect band overlap
Brad Malone
brad.malone at gmail.com
Tue Dec 1 01:04:01 CET 2009
As a follow up on my previous post, I let the calculation run to completion
on a less dense k-grid and saw the following output:
ik 2 ibnd 17 linter: root not converged 0.748E+35
> kpoint 2 ibnd 17 pcgreen: root not converged 0.421E+23
> Non-scf u_k: avg # of iterations =137.0
> Non-scf Du_k: avg # of iterations =200.0
>
> Dielectric constant from finite-differences
>
> ( NaN NaN NaN )
> ( NaN NaN NaN )
> ( NaN NaN NaN )
>
> Computing Second order response
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
>
>
> iter # 1 av.it.: 147.2
> thresh= 0.100E-01 alpha_mix = 0.100 |ddv_scf|^2 = NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
> kpoint 2 ibnd 17 pcgreen: root not converged NaN
>
>
> iter # 2 av.it.: 200.0
> thresh= 0.100E-01 alpha_mix = 0.100 |ddv_scf|^2 = NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
> kpoint 1 ibnd 17 pcgreen: root not converged NaN
>
>
> and so on. The code crashes at the end with the error:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> from broyden : error # 1
> factorization
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
>
but obviously the problem occurs well before this crash. Again, I am trying
to calculate the Raman intensity for a material with a small indirect
overlap. Should this not be possible? I know that DFPT is applicable
(without modification) only for systems with a clear distinction between
occupied and valence states (in order to clearly specify what the projectors
over the occupied and unoccupied manifolds I guess?). For the indirect
overlap case with fixed occupancies I would imagine that this would be
possible.
Anyway, just wanted to report on the results of my first post. If anyone
knows what I can do to calculate the intensity or simply if it should or
shouldn't work (and/or "why") I would greatly appreciate it.
Best,
Brad Malone
UC Berkeley
On Sun, Nov 22, 2009 at 11:36 AM, Brad Malone <brad.malone at gmail.com> wrote:
> Hi, I'm interested in calculating the Raman intensity for a material with a
> small indirect band overlap within LDA (~0.3 eV). As has been mentioned many
> times on this forum, Raman intensities cannot be calculated for a pure
> metal. But should I expect to be able to calculate the intensity for a
> material with a small, indirect band overlap? When I attempted to do so
> (using lraman=.true. in the ph.x calculation) I received the following
> messages:
>
> Computing Pc [DH,Drho] |psi>
>>
>> Derivative coefficient: 0.001000 Threshold: 1.00E-12
>> ik 1 ibnd 17 linter: root not converged 0.578E+08
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.763E+05
>> ik 1 ibnd 17 linter: root not converged 0.193E+11
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.119E+05
>> ik 1 ibnd 17 linter: root not converged 0.595E+09
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.182E+05
>> ik 1 ibnd 17 linter: root not converged 0.142E+31
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.224E+24
>> ik 1 ibnd 17 linter: root not converged 0.143E+30
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.170E+25
>> ik 1 ibnd 17 linter: root not converged 0.765E+28
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.151E+25
>> ik 1 ibnd 17 linter: root not converged 0.643E+09
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.460E+05
>> ik 1 ibnd 17 linter: root not converged 0.619E+10
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.547E+07
>> ik 1 ibnd 17 linter: root not converged 0.685E+09
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.810E+04
>> ik 1 ibnd 17 linter: root not converged 0.290E+34
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.848E+19
>> ik 1 ibnd 17 linter: root not converged 0.132E+33
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.333E+18
>> ik 1 ibnd 17 linter: root not converged 0.155E+34
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.133E+20
>> ik 1 ibnd 17 linter: root not converged 0.146E+06
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.442E+05
>> ik 1 ibnd 17 linter: root not converged 0.135E+07
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.169E+06
>> ik 1 ibnd 17 linter: root not converged 0.567E+08
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.493E+06
>> ik 1 ibnd 17 linter: root not converged 0.292E+27
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.518E+23
>> ik 1 ibnd 17 linter: root not converged 0.882E+28
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.215E+24
>> ik 1 ibnd 17 linter: root not converged 0.104E+29
>> kpoint 1 ibnd 17 pcgreen: root not converged 0.328E+23
>> ik 2 ibnd 17 linter: root not converged 0.585E+21
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.363E+23
>> ik 2 ibnd 17 linter: root not converged 0.505E+21
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.119E+22
>> ik 2 ibnd 17 linter: root not converged 0.117E+21
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.267E+22
>> ik 2 ibnd 17 linter: root not converged 0.159E+33
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.283E+27
>> ik 2 ibnd 17 linter: root not converged 0.367E+32
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.660E+27
>> ik 2 ibnd 17 linter: root not converged 0.876E+32
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.670E+28
>> ik 2 ibnd 17 linter: root not converged 0.249E+32
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.125E+28
>> ik 2 ibnd 17 linter: root not converged 0.348E+31
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.206E+26
>> ik 2 ibnd 17 linter: root not converged 0.141E+30
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.561E+25
>> ik 2 ibnd 17 linter: root not converged 0.520E+36
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.990E+24
>> ik 2 ibnd 17 linter: root not converged 0.140E+37
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.721E+24
>> ik 2 ibnd 17 linter: root not converged 0.836E+35
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.690E+25
>> ik 2 ibnd 17 linter: root not converged 0.246E+30
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.540E+24
>> ik 2 ibnd 17 linter: root not converged 0.517E+29
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.415E+25
>> ik 2 ibnd 17 linter: root not converged 0.133E+30
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.202E+26
>> ik 2 ibnd 17 linter: root not converged 0.570E+27
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.103E+21
>> ik 2 ibnd 17 linter: root not converged 0.270E+29
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.451E+22
>> ik 2 ibnd 17 linter: root not converged 0.381E+29
>> kpoint 2 ibnd 17 pcgreen: root not converged 0.346E+22
>> ik 3 ibnd 17 linter: root not converged 0.118E+34
>>
>
> and so on for each ik in the calculation. The code never crashed and I
> stopped it prematurely due to concern about these messages (seeing values on
> the order of 1E+34 is never calming). The code was also taking a very long
> time to calculate each ik. From what I've read in the Lazzeri and Mauri
> paper (PRL 90, 036401, 2003) some of the methods used to calculate the Raman
> tensor can take a lot of linear response calculations and so maybe I
> shouldn't expect it to go extremely fast. However, this root convergence
> worries me. The 17th band, which is the only band that this problem occurs
> for that I've seen, is the first conduction band of the system and is the
> band that indirectly overlaps with the top of the valence band. Any help or
> comments would be greatly appreciated!
>
> Thanks,
> Brad Malone
> UC Berkeley
>
> P.S. I used 'fixed' occupancies in the SCF run to avoid the 'elec. field'
> error in the ph.x calculation. The fixed occupancy is what I would expect
> for this material in experiment, as the GW bandstructure for this material
> predicts it to be semiconducting.
>
>
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