[Wien] Testing convergence with size for a surface

[L. D. Marks]

I want to check the convergence of a surface calculation versus the slab 
thickness. The obvious way is to calculate the difference
 	E_diff = E_slab2 - E_slab1 - n*E_bulk
where slab2 has n more layers than slab1. Unfortunately there is a problem 
with this. For a conventional small cell bulk calculation, RKMAX is 
rounded down (exact size depending upon the k-vector), so it's not 
completely obvious what the RKMAX for the slabs should be and this can 
make a big difference. I tried plotting E_bulk versus RKMAX and 
interpolating, but I don't think I believe the results.

Has anyone worked through this in detail to find a viable method?

Note: if you have an old email address for me, please note that "nwu" has
been changed to "northwestern".
-----------------------------------------------
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60201, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
http://www.numis.northwestern.edu
-----------------------------------------------