Hirshfeld charge of MoS2 in cp2k

[anyu...@gmail.com]

Dear all,

I run the cell_opt  for 4x4x1 MoS2 system and I want to analyze the Hirshfeld charges, the result shows the Net charge of Mo and S are -1.243 and 0.622, respectively.  But I thought the charge of Mo should be positive while S should be negative. 

Can anybody help me to see if there are any problems or I misunderstood it?  Thank you very much in advance.

Kind regards,

Yun

[Gabriele]

Dear Yun,

You can try to compute the charges using self-consistent hirshfeld partitioning (use SELF_CONSISTENT T inside the section &HIRSHFELD..&END) and using SHAPE_FUNCTION DENSITY. It has been highlighted before that there is in general a dependence of the charges on the basis set on MoS2 (see https://groups.google.com/forum/#!topic/cp2k/gZgiyqZURs4)

For the DZVP-MOLOPT-SR basis, setting self consistent partitioning will give the right sign of the charges. We have also noticed that using this scheme there is not a significant dependence of the charges wrt to the size of the basis set. However, it is worth checking the dependence on the basis set size of the geometry and of other properties that may be relevant for your specific case.

For that, you may want to check the file BASIS_MOLOPT_UCL, which is an extended molopt basis set library.

https://sourceforge.net/p/cp2k/code/HEAD/tree/trunk/cp2k/data/BASIS_MOLOPT_UCL

Best

Gabriele

[anyu...@gmail.com]

Dear Gabriele,

Thank you very much for the kind reply! I tried rerun the calculations with your suggestions(I used the self-consistent hirshfeld and shape function density, also the new TZVP basis for Mo ), now it gives the Net charge for Mo 0.319 and -0.160 for S. Is this means the basis set on Mo is stronger than S? I'll rerun several tests. Thank you again.

Best,

Yun
在 2017年11月20日星期一 UTC+1下午3:55:53，Gabriele写道：

[Gabriele]

Hi Yun,

It might be because the Mo basis set is effectively larger than the S one. For instance, if you were to use a SZV-MOLOPT-SR for Mo and DZVP-MOLOPT-SR for S and look at the mulliken charges you would see that the signs are also correct, while they are wrong if you use DZVP for both elements. I am not suggesting to use a SZV for production though. The point on the mulliken charges is just to illustrate the effect of a different basis set size for the two elements.

Best

Gabriele