przemek
Hello,
I have defined the double occupancy at the same site. However I keep receiving slightly different results depending if the both elements are defined in two separated lines:
site T(1) x 0 y =y1; z =z1; occ Si =1-ppAl; beq 1
site T(1a) x 0 y =y1; z =z1; occ Al =ppAl; beq 1
or by the single line:
site T(1) x 0 y =y1; z =z1; occ Al =ppAl; occ Si =1-ppAl; beq 1
The difference is mostly shown by the different esd's of the occupancies which are important for me. In my understanding both ways should give exactly the same results. Does anyone have any idea why is different?
Thanks in advance for any help.
Best regards,
Przemek
johnsoevans
Dear Przemek,
I think this is because you need to tell topas a beq value for each atom on each site in this format. i.e. you need to say "occ Al - ppal; beq 1 occ Si = 1-ppal; beq 1" in your example. If you don't do this I think the default is that the first occ listed just defaults to having beq 0. Obviously in general you would equate the beq values for the two different occupancies.
I don't remember if that's spelt out in techref, but the examples in there have this format.
I haven't checked this, so do post again if that's not the answer.
Best,
John
przemek
Dear John,
Your suggestion solves the problem. Esds are exactly the same now.
Thank you for your help.
Best regards,
Przemek