Recent content by bsmile

My two cents, mathematically, it's basically an energy expression expanded in terms of six degree of freedoms to the 2nd order of geometry changes (those e_i). Since the solid is stable, thus 1st term vanishes, only the quadratic term is left. The derivative of (free) energy w.r.t geometry...

Thanks, I understand here ##\psi## is a scalar, thus a geometric transformation does not change it, while dot product being a scalar is also not affected. What if ##\psi## is a spinor with its axis along discrete z direction while the target K has a direction arbitrary in space, or another...

Yes, I understand there is point group symmetry operation on how to related one K point to the other equivalent ones, but I don't know how to transform the eigen-wavefunction for (n,K) where n is band indices? I believe this could be done. A further question is, would the transformation depend...

sorry, I should be more careful towards my terms, it should be something like irreducible K wedge in the first Brillouin Zone.

In ab initio calculations for periodic systems, only an irreducible K grid is used for calculation, and consequently only those K points have their wavefunction calculated. My question is, how to recover wavefunction at other K points not included in the irreducible K grid? Similar questions to...

Anybody familiar with bilbao (http://www.cryst.ehu.es/#structuretop)? Anybody knows how to use one of the Structure Utilities, CELLTRAN?

I tried VESTA, and dragged the primitive cell to different orientations, and then output the structure to files, but found no change in the atomic positions. Maybe I did something wrong, if anybody knows how to do so with VESTA and let me know where I did anything wrong, I would be really...

Dude, thanks for your response anyway. Everybody learned linear algebra and I know it pretty well. For these well-developed topics and industry-like ab initio calculation, there should be ready tools existing to free individuals from detailed manipulation of matrices and close attention to avoid...

In case the orientation of a primitive cell is not what I want, is there tools to do a user-supplied 3D rotation to bring the primitive cell to the preferential orientation and output the new coordinates? Thanks,

Thank you very much! This really helps.

Experimentalists usually provide chemical unit cell information including full symmetry (space group) information of the crystal together with coordinates of independent atoms. But this cannot be directly used by ab initio packages, which requires either primitive cell or unit cell information...

One thing I might mention is that the lack of accuracy can be in NIntegrate as well as it might fail to reach prescribed precision goal I set. I have written to Mathematica to see whether there is way to detect the condition satisfied or not.

Thanks, I had been clicking on the figure icon on top of the textbox, and it really didn't do what I wanted. Here is the figure showing the two otherwise equivalent expressions have error bigger than machine precision and has a strong dependence on the input parameters. I understand the...

Thanks for your help. I wonder whether the issue comes from Log[z/(z-1)]. To test it, I evaluated two equivalent expressions with Mathematica making use of the following identity ln(z/(z-1))=∫^{1}_{0} 1/(z-x) dx Ideally, the difference between left and right hand sides should be zero, but...

The expression to code is: (z complex, m some positive integer) z^m ( ln(z/(z-1)) - sum( 1/(k z^k), {k=1,m} ) ) The way I code is (in fortran) (in case z<2) Z_1=1.0_q/Z ZV1=LOG(Z/(Z-1)) ZK=1.0_q DO K=1,M; ZK=ZK*Z_1 ZV1=ZV1-ZK/K ENDDO ZV1=ZV1/ZK But it gives quite big error...