[Pw_forum] spin polarised STM

[Guido Fratesi]

Dear Madhura,

> 1. While calculating STM image, is sum taken over both the spin
> channels? Because there is no option for spin resolved calculations,
> and in the subroutine I was not able to find where sum is done. 

Yes it is. The sum is taken over all k-points, regardless of the spin this 
kpoint correspond to (as you know, in pwscf spin "up" and spin "down" are 
treated as two sets of kpoints).

> 2. Does anyone have a subroutine to get spin-polarized STM image? If
> yes, can you send it?

You might consider using again pp.x to plot the ILDOS in the corresponding 
energy range, for which you can specify the spin component. Although the 
weight of states contributing to ILDOS and STM is not computed exactly in 
the same way by pp.x, you should expect the results to become equivalent 
as the number of relevant states falling in the energy interval is 
sufficiently large (see, number of kpoints & slab thickness).

> 3. Or if not, can anyone tell which part of code needs to be modified
> to get SP-STM image?

At line 150 of PP/stm.f90, "DO ik = 1, nks". You could restrict this 
summation to states with wanted spin, or accumulate the two sums 
independently. The spin of each kpoint is stored in isk(ik). See its use 
in projwfc.f90 for examples.

HTH

-- 
Guido Fratesi

Dipartimento di Scienza dei Materiali
Universita` degli Studi di Milano-Bicocca
via Cozzi 53, 20125 Milano, Italy