My code to calculate non-linear response in solids and nanostructure is finally online.

The first tutorials are available, and soon I will finish the other ones.

Full free to use it and let me know if you find bugs or strange things.

My code to calculate non-linear response in solids and nanostructure is finally online.

The first tutorials are available, and soon I will finish the other ones.

Full free to use it and let me know if you find bugs or strange things.

WENSHEN SONGHello,

I try to do SHG calculation in lumen, but I cannot find a forum for lumen so I ask questions here. I wonder how to set the direction for the SHG tensor chi. As far as I am concerned, Chi_ijk could be expressed as P_i=Chi_ijk E_j E_k, so how can we determine the i,j and k in lumen? I read the tutorial for lumen SHG in AlAs, and the external field is set as

ExtF_Dir

1.000000 | 1.000000 | 0.000000 |

Does it mean setting j=x and k=y? And the output for x,y,z directions should give Chi_xxy, Chi_yxy, Chi_zxy? If so, why does the tutorial plot give a label as Chi_xyz?

attaccPost authorDear Wenshen

thank you for interesting in Lumen.

I will add a Forum to Lumen soon ðŸ™‚

>

> I wonder how to set the direction for the SHG tensor chi. As far as I am concerned, Chi_ijk could be expressed as P_i=Chi_ijk E_j E_k. So, how can we determine the i,j and k in lumen? I read the tutorial for lumen SHG in AlAs, and the external field is set as

> ExtF_Dir

> 1.000000 | 1.000000 | 0.000000 |

in this example there is only one field, therefore E_j=E_k.

> Does it mean setting j=x and k=y?

Yes the three numbers in the input are the x,y z direction, I modified the tutorial to make it clear

> And the output for x,y,z directions should give Chi_xxy, Chi_yxy, Chi_zxy? If so, why does the tutorial plot give a label as Chi_xyz, for which should actually be Chi_zxy?

In this example we calculate Chi_zxy but in AlAs Chi_zyx=Chi_xyz=Chi_yxz

see also Eq. 24 in https://journals.aps.org/prb/abstract/10.1103/PhysRevB.82.235201

I modified the tutorial to make this point clearer this point and corrected the figure

Yours

Claudio