ABINIT Discussion Forums

Dear All, The van der Waals functional has been mentioned in the features of Abinit for a long time, and three test files are also included under tests/vdwxc. Recently, I replace the Ar molecular crystal in tests/vdwxc/Input/t01.in (ixc=-102, vdw_xc=1, 2) with graphite but found that the A and B lay...

Dear All, Similar to the case I discussed in another post with Matthieu (http://forum.abinit.org/viewtopic.php?f=10&t=1261), this problem is also related to the NSCF WFK by iscf=-2, which gives incorrect occupations and causes incorrect electron transitions. When I use iscf=-3 to generate the NS...

Dear All, I disscussed the problem with Matthieu in another post, and as him pointed out, the occupations in SCF and NSCF WFK are different. After switching iscf=-2 to iscf=-3 (the later initializes occ and wtk), I got correct optical spectra. The cause could be the incorrect band filling in the WFK...

Dear Loniarf, I use Intel Ifort-9.1.052 and Intel mpi 4.0.0.028 to compile ABINIT, and they worked pretty well for the abinit versions I used. The following line is my configure setting for abinit-6.8.1. ./configure FC=/opt/intel/impi/4.0.0.028/bin64/mpiifort enable_mpi=yes --enable-mpi-io=no --enab...

Dear Matthieu and Zwanziger, Thank you both for the information. As Matthieu pointed out, the occupations in SCF and NSCF WFK are different. After switching iscf=-2 to iscf=-3 (the later initializes occ and wtk), I got correct optical spectra again! So the cause could be the incorrect band filling i...

Dear loniarf,

I analyzed the ddb file and received no segmentation fault, but there are lots of "NaN" in the output file. You could run the test packages to make sure if there is any problem with your compilation.

Sincerely,
Guangfu Luo

Dielectric function contains all the necessary information. Check some textbook to find out their relationships with others.

Guangfu Luo

(1) Switch to metallic occupation with small tsmear

(2) Use nbdbuf to speed the convergence of tolwfr

(3) Update to the latest Abinit, which improves a lot on speed according to my experiences

Sincerely,
Guangfu Luo

Dear Prof. Zwanziger, Thanks for your suggestion. But it is embarrassing that I do not know how to easily do a finite difference check on the ddk of wavefunction. However, I did another test and find that the problem could be in the final optic analysis code rather than the ddk calculation. Since in...

Dear Prof. Zwanziger, Thanks for your reply. Actually, I followed the same procedures to do ddk calculation as the tutorials, and did get correct results for many systems. But in the 1D chain systems, I happened to notice that the usual procedure gave wrong results, which are confirmed by other prog...

Dear developers, As I mentioned earlier (http://forum.abinit.org/viewtopic.php?f=10&t=1153), I found that ABINIT (both 6.2.2 and 6.8.1) gives wrong linear optical spectrum in several 1D systems by using the usual procedures. Here I elaborate this issue with a simple example of carbon chain. The ...

Dear developers, As I mentioned earlier (http://forum.abinit.org/viewtopic.php?f=10&t=1153), I found that ABINIT (both 6.2.2 and 6.8.1) gives wrong linear optical spectrum in several 1D systems by using the usual procedures. Here I elaborate this issue with a simple example of carbon chain. The ...

I think you should tighten the convergence parameter together with a larger nstep. I use "tolwfr 1.0d-22" and "nstep 1000".

Additionally, is you geometrical structure fully relaxed? I use "tolmxf 1.85d-6" in such calculation.

Sincerely,
Guangfu Luo

Dear developers, In a phonon band structure calculation, if ABINIT is stopped before a DDB files is produced, there is no easy way (I think) to reuse the useful written results but restarting the DATASET from ground. I encounter this issue several times and it is really disappointing. According to l...

I happened to calculate the phonon dispersion of cubic ZrO2 before and the results are consistent with earlier literatures. The attached are the input files for both the geometrical optimization and phonon dispersion calculation. (Hope this late reply could be useful for the future searcher.) Sincer...

Maybe this post is helpful. viewtopic.php?f=10&t=92

Sincerely,
Guangfu Luo

Dear developers, While testing the GW calculation in Abinit-6.8.1, I found a job finished successfully earlier in Abinit-6.2.2 failed in the screening calculation part with the following error (see the attached test file). I checked cchi0q0.F90 and found that since Abinit 6.6.1, cchi0q0.F90 has incl...

Dear Peiman,

I tested your file in ABINIT 6.8.1 and got the final results. The problem should be with your MPI or compilation.

Sincerely,
Guangfu Luo

PAW can be used in the linear optical response calculation and gives almost the same converged results as NCP according to my tests. I find using PAW reduce the CPU time only a little but the memory consumption a lot.

Sincerely,
Guangfu Luo

Dear xiangpisai, Most of the time, a segmentation fault means lack-of-memory. You can test this by monitoring the memory consumption. In a screening calculation, "gwpara 2", "gwmem 0", and using PAW can greatly reduce the memory use. The "gw_eet" and "gw_EET_nband&...

Dear developers, I test the optical spectrum of graphene and surprisingly find that Abinit gives totally wrong spectrum with shiftk=(0,0,0). While with the default shiftk=(0.5,0.5,0.5), Abinit gives consistent result with Yambo and CASTEP. Increasing the ngkpt does not change this situation. This is...

Dear Matthieu,

Actually, I tried a different system with hexagonal symmetry and also got consistent result with that from CASTEP (the intensity however differs by a constant).

Sincerely,
Guangfu Luo

Dear Peiman,

I did such calculation before and the attached is my input file for your reference.

Sincerely,
Guangfu Luo

Dear Matthieu, I did my tests this way to toptic_3.in. First, I increase ecut to 4 (just in case). Then I compare the final results (optical spectra) between kptopt=1 and kptopt=2 with different ngkpt (4x4x4, 24x24x24, and 36x36x36). The tests show that different kptopt options display major spectru...

Dear Developers, Comments in toptic_3.in indicate that only Time-reversal symmetry can be used in a ddk response calculation. However, after doing several tests by using Abinit-6.2.2 I found these comments to be obsolete: using kptopt=1 will not cause a program abortion and it gives nearly the same ...