2 thoughts on “Lumen code is online!

  1. WENSHEN SONG

    Hello,
    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?

    Reply
    1. attacc Post author

      Dear Wenshen

      thank you for interesting in Lumen.
      I will add a Forum to Lumen soon 🙂
      >
      > 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

      Reply

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