Band Edge Alignment

Chhatra

Dear CRYSTAL developers and users,

I would like to perform a band edge alignment calculation by referencing the valence/conduction band edges to the vacuum level in the context of photocatalysis. For this purpose, I need the planar-averaged electrostatic potential along the slab normal direction.

I have already generated the electrostatic potential in Gaussian cube format using the POTCUBE keyword (file: POT_CUBE.DAT).

My questions are:

Does CRYSTAL provide any direct tool or utility to compute the planar average of the electrostatic potential from POT_CUBE.DAT (or other related output files)?

If not, is it recommended to post-process the cube file externally (e.g., with scripts, VESTA, or custom Python routines)?

Any guidance, example workflows, or scripts would be greatly appreciated.

Best regards,
Chhatra Subba

mriveraa

Dear Chhatra,

There is the POTC keyword (page 352 of the CRYSTAL23 manual). You can also refer to this tutorial, where there is an example of its usage. I would suggest using this instead of performing post-processing of the 3-dimensional cube file.

Let me know if this helps you!
Best regards,
Marcos

Chhatra

Thank you so much for your response. I tried it, but it shows an error

GCALCO - MAX INDICES DIRECT LATTICE VECTOR 29 29 3
NO.OF VECTORS CREATED 6999 STARS 3500 RMAX 122.19169 BOHR
TTTTTTTTTTTTTTTTTTTTTTTTTTTTTT gordsh1 TELAPSE 0.05 TCPU 0.02

MATRIX SIZE: P(G) 377103, F(G) 76624, P(G) IRR 193585, F(G) IRR 78287
MAX G-VECTOR INDEX FOR 1- AND 2-ELECTRON INTEGRALS 321

CAPPA:IS1 8;IS2 8;IS3 8; K PTS MONK NET 260; SYMMOPS:K SPACE 2;G SPACE 1

PLANE AVERAGED ELECTROSTATIC POTENTIAL
N. OF POINTS 201 ZMIN -20.000 (AU) - ZMAX 20.000 (AU)

**** LDIM, ICASO= 4 2
ERROR **** POTCAL **** CASE NOT AVAILABLE
Abort(1) on node 2 (rank 2 in comm 0): application called MPI_Abort(MPI_COMM_WORLD, 1) - process 2

Does this method only work for SLAB systems created using CRYSTAL17’s SLABCUT utility or SLAB keyword used in input geometry block? My present work involves a 2D material slab, but I generated the slab structure using VESTA and modeled it in CRYSTAL keyword in input block with a 15 Å vacuum along the z-direction

mriveraa

Yes, as indicated in the manual: Plane and volume averaged properties can be computed for slabs (2D) only. If you can use instead the SLAB keyword, then it should work. Otherwise, I think post-processing the cube file would be the option, which maybe someone else can give you advice with (I think it can be easily performed with Python, given it follows the standard format, and even not hard to request to a generative-AI solution). If you want to go for the SLAB option, you can also ask here if you get any trouble.

Best,
Marcos

Chhatra

Sure. I will try it. Thankyou so much.