I'm reposting here a message that I mistakenly sent privately to Brad: have a look at the total-energy components: if the one-electron contributions increases at the expenses of the other terms (mostly the hartree term) than you have found a ghost in the pseudopotential. As far as I know, all non-local separable pseudopotentials have ghost states for large enough values of the curoff.
I'm not really sure my impression is correct, but I've always had problems with large enough cutoffs with any pseudopotential I have tried. My rationale is more or less on this line: the pseudopotential only have Fourier components up to a certain threshold; plane waves over that threshold do not feel any direct effect from the ions. As a consequence this very high frequency plane waves gain nothing by forming a charge density close to the ions, instead they can just spread around to minimize the Hartree energy (which decreases) at the expenses of kinetic energy (which increases). cheers -- Lorenzo Paulatto SISSA & DEMOCRITOS (Trieste) phone: +39 040 3787 511 skype: paulatz www: http://people.sissa.it/~paulatto/ *** save italian brains *** http://saveitalianbrains.wordpress.com/ ---------------------------------------------------------------- SISSA Webmail https://webmail.sissa.it/ Powered by Horde http://www.horde.org/
