[Pw_forum] Pseudopotentials for Pseudo-Hydrogens

[Vic Bermudez]

Hello,

	I'm setting up a slab calculation for the GaSb (100) surface using PW91
USPP's for Ga and Sb. I want to passivate the "bottom" (Ga-terminated)
surface with pseudo-hydrogens, which will require two Z=5/4 pseudo-H's per
Ga. However, the QE website gives only PZ pseudopotentials for pseudo-H's.
	Here's my question. I know that it's problematic to mix different kinds of
PP's in the same calculation, and, of course, pw.scf gives a fatal error
when I try. Will I get into trouble if I override this by using
input_dft='pw91', so that I can use the PZ PP's for the pseudo-H's ?  I'm
interested mainly in adsorption energies, which are the differences in
energies between bare and adsorbate-covered slabs. Will any errors incurred
by mixing PP's cancel in the difference.
	As always, thanks for your help and advice.

Victor M. Bermudez
Code 6876
U.S. Naval Research Laboratory
4555 Overlook Ave., S.W.
Washington, DC 20375-5347

Phone: 202-767-6728
FAX: 202-767-1165
E-mail: victor.bermudez at nrl.navy.mil