Hello, Thanks for replying me.
Could you please let me know: 1. how you show the basis of the ghost atom in the input file? 2. If we have 3 different types of atoms in the unit cell, let's say BaTiO3, how dowe consider the ghost atoms then? Regards, Sarah On Thu, Feb 12, 2009 at 4:05 PM, R.C.Pasianot <pasia...@cnea.gov.ar> wrote: > Hello Sarah, > > Never did that type of calculation, so please sages out there > correct me if I'm wrong ... > > Let say you want to calculate Fe, which is bcc. > 1st, perform a calculation with the standard, cubic, two atoms > unit cell. > 2nd, perform the same calculation (keeping lattice parameter, > basis, etc) but putting ghosts at the vertices, namely, keeping > only the atom at the center. > Finally, compare the two and you'l get the cohesive energy. > > Best, > > Roberto > > > On Thu, 12 Feb 2009, Sarah Lebedev wrote: > > *I am very sorry to re-send my email, but I really need to know the >> answer.* >> >> >> >> Dear Siesta users, >> >> I am sorry, I have not got my answer reading the whole archive about this >> subject. Therefore, I hope you would kindly let me know the answer of the >> following question: >> >> We all know that for the crystals we have the following relation: >> >> *Cohesive Energy (CE) = (energy of free atom) - (energy of atom in a >> crystal).* >> >> I am working on GaN bulk and nanostructures. >> >> 1. Regarding the energy of the free atom, as I read the archive, it seems >> that we have to consider the ghost atoms surrounding the main atom to get >> the enrgy of the free atom?! or, it is enough to have the right basis of >> the >> atom and calculate its energy? >> >> 2. energy of atom in a crystal: when we calculate the enery of the bulk, >> then how do we have the energy of the atom in the structure? >> >> 3. I would be grateful if you let me know the additional terms I have to >> consider in order to calculate the cohesive energy of a slab too. >> >> Regards, >> Sarah >> >>
