| Re: Elastic Constant of Cu - 6.0Hs3p3d3 ( No.1 )|
- Date: 2019/06/20 23:51
- Name: T. Ozaki
In a dense structure such as FCC, HCP, and BCC with a small lattice constant,
eigenvalues of overlap matrix approach to zero, and sometime they become even negative
values. The situation is called overcompleteness of basis functions, and a numerical
instability may appear. Then, changing parameters such as temperature, k-points, and scf
criteria does not resolve the overcompleteness.
Reducing the basis functions can solve the problem.
I wonder that s3p3d2 works well for your purpose.
| Re: Elastic Constant of Cu - 6.0Hs3p3d3 ( No.2 )|
- Date: 2019/06/21 20:14
- Name: C. Pashartis
- Hello Prof. Ozaki,
Thank you for your response. For the most part, I have been following the basis set schemes that your project has shown on the website in comparison to WIEN2K for the equation of state (varying lattice and plotting energy). I believe this to be a good starting spot for my calculations given that I deform my structure in a non-isotropic fashion.
I believe the over-completeness to still be occurring for s2p2d2, am I correct in assuming that the s3p3d2 should then not work either? What are my other options given that it seems the s2p2d2 scheme won't work either?
I did also try s3p3d3 on the soft version, however, the results aren't as accurate in elastic properties compared to literature. Which can be inferred from the difference in the equation of state to WIEN2K.