Dear All,
I am calculating the total energy of a gold sample after relaxing at 0K for different boundary conditions.
Size of the sample is 20 x 20 x 10 lattice constants
Boundary condition Total energy (eV)
ppp 62880
pps 65263.48
The total energy of the sample for pps should be greater than ppp as pps has free surface. But in my case it is not so. Does anyone has any clue.
Thanks
Sivashankar

Could be any number of reasons. Maybe with a free surface, the entire
sample relaxed and lowered the energy. That won’t happen in a periodic
system.
Steve
Dear All,
I am calculating the total energy of a gold sample after relaxing at 0K for different boundary conditions.
Size of the sample is 20 x 20 x 10 lattice constants
Boundary condition Total energy (eV)
ppp 62880
pps 65263.48The total energy of the sample for pps should be greater than ppp as pps has free surface. But in my case it is not so. Does anyone has any clue.
your reasoning doesn't make much sense.
with ppp you can have interactions between periodic images
in zdirection, with pps not. whether those interactions are of
positive or negative energy depends on your input and the
choice of potentials and cutoffs.
cheers,
axel.