Hi all,

We would like to be able to calculate the vibrational properties of solid solutions

for example, A_(1-x)B_xO. We assumed that this would involve creating a supercell in the *.gin file and then inputting the appropriate concentration of A,B atoms.

However we foresee a problem that is illustrated by example 5 - MgO. Our approach assumes that doubling the unit cell size of the MgO (hence cubing the number of atoms in the unit cell) would result in identical dispersion curves to MgO itself. However the larger unit cell gives different dispersion! In addition both example 5 which assumes a=4.212 with an 8 eight atom basis and example 5 assuming unit cell size 2a=8.414 angstroms with 32 atom basis give the incorrect number of dispersion branches (which should be 6).

Any ideas as to what we are doing incorrectly? Was our original idea wrong?

David