Paolo, The smearing flag solved the problems. Thank you much for the tip (on behalf of myself and my class). I agree this is an excellent teaching exercise. Mark Asta suggested it to me, and it seems perfect.
I still believe that there are 2 atoms per unit cell in the beta-Sn structure, so I am a bit confused by your final statement. I suppose this depends on the choice of lattice vectors... Daryl Daryl C. Chrzan Professor, Materials Science and Engineering University of California Berkeley, CA 94720 and Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley, CA 94720 ph./fax: 510 643 1624
