[DFTB-Plus-User] d orbital order {hh(4, 1) element for "subroutine dd" in lib_dftb/sk.F90}

Bálint Aradi aradi at uni-bremen.de
Fri Sep 23 17:43:50 CEST 2016

Dear Sharma,

> Thank you. I understood that you are using rotated tesseral (real) 
> spherical harmonics and for p-orbitals, I was able to match the 
> equations with the subroutines. I want to know the order of 
> dxy,dyz,dxy,dx2-y2,dz2 in the current implementation in terms of 'm'
>  (=-2,-1,0,1,2). Based on the equations in the paper,  dxy=-2, 
> dyz=-1, dzx=1. I am assuming dz2=0 and dx2-y2=2. Could you please
> let me know whether this order is correct or not?

I think, the order should be xy, yz, z2, xz, x2-y2.

> Also, would it be possible to you to tell me on how do you decide
> this kind of order, apriori (I have seen textbooks with different
> orders, and hence, the question)?

The one programming the SK-transformation routines in DFTB+ decided for
a given order. Since it appears in the code at exactly one place only,
the choice of the order is not really a relevant issue.

Best regards,


Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen

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