The SHG component was incorrectly calculated

[sunxl]

Dear all,
According to the symmetry analysis, the second-order nonlinear susceptibility tensor of the material I calculated in the zyy direction should not be zero, and the xyy and yyy directions should be zero, but when I calculate with IPA, set

% Field1_Dir
0.000000 | 1.000000 | 0.000000 |

In the end, I got the opposite results. zyy direction is zero, xyy and yyy are not zero. Is there a problem with symmetry in setting the lattice constants and atomic coordinates? I appreciate any guidance and tutorial on that!

Best,
sunxl

[claudio]

Dear sunxl

I'm not aware of particular problems with symmetries, please provide us more information on your systems, and so on.
Consider that due to numerical noise SHG is never completely zero, but vey very small

best regards
Claudio

[sunxl]

Dear claudio
Thanks for your reply.

The system I calculated is a two-dimensional material belonging to space group 156, p3m1, with four non-zero independent components, Xzyy, Xyzy, Xzzz, and Xxxy. No matter what direction I set the external electric field Field1_Dir, I get results with zero components in the z direction, which seems to be wrong.Because according to my symmetry analysis, the Xzyy and Xzzz directions should have a result.

The content provided in the attachment relates to the input files used for calculating the Xzzz.

Best,
sunxl