Hi Ian, Most probably siesta differentiates between bulk, slabs, molecules and atoms by checking a minimum distance of vacuum between the images in the three cartesian or crystallographic directions - I am not sure as to how much this minimum distance would be, but I guess the manual can provide some hint. Otherwise, the code itself has this minimum distance set somewhere in it.
Perhaps all you want to know is stated in the paper The Siesta method for ab initio order-N materials simulation José M. Soler, Emilio Artacho, Julian D. Gale, Alberto García, Javier Junquera, Pablo Ordejón and Daniel Sánchez-Portal J. Phys.: Condens. Matter 14, 2745-2779 (2002) arXiv:cond-mat/0111138, 8 Nov 2001. which is the most updated description of the method. Hope this helps. Best regards, Marcos > Marcos > > I agree with your comments about cutoff and BZ. > > I dont understand your comment about the difference between slab and bulk > system, though - how does changing the units alter this? And how does > siesta treat the two systems differently? The only reference I can find to > slabs is on page 21 of the manual which show how to fix ion core positions > (which seems like a bit of a cheat). > > I am real curious to know how siesta trreats periodicic cells though - > does it fix first derivatives at the boundaries for example. Maybe not... > > Thanks > > Ian > -- Dr. Marcos Verissimo Alves Post-Doctoral Fellow Condensed Matter and Statistical Physics Sector International Centre for Theoretical Physics Trieste, Italy -------- I have become so addicted to vi that I try to exit OpenOffice by typing :wq!
