[gpaw-users] An error occurs when performing STM simulation using GPAW

[Christian Glinsvad]

I wrote:
> That doesn't make sense to me. This is an issue with too little
> vacuum  in the z-direction as far as I can tell from the code.

Actually, it does. AtomCenteredFunctions in gpaw/transport/jstm.py
creates a smaller and completely non-periodic grid to contain each
LocalizedFunctionCollection (i.e. LCAO basis function) and the way it
determines the minimum required box size might be a little buggy.

> For the record, here's my slightly altered (read optimized) surface.py:
> http://en.pastebin.ca/1901965

I had forgotten to revert the (3,1,1) repetition for fcc110 etc. With
the patch and the following surface.py, I get the error you reported.
http://en.pastebin.ca/1901995

The shapes on lines 161 and 162 in ase/transport/stm.py are:
v_12: (298, 15), a2: (55, 55), a2[:dim1]: (15, 55) with dim1=15
v_21: (15, 298), a1: (178, 178), a1[-dim0:]: (178, 178) with dim0=298

So apparently, the Hamiltonan for the tip region (i.e. "a1") is too
small compared to the number of bands (298) for the surface region,
or conversely, that you're including too many bands for the surface.
Try running the surface calculation with nbands=-50 or similar.

Regard
Christian Glinsvad