regarding stress calculations

[Pawandeep Kaur]

hello everyone,
i wanted to find out stress with extended huckel model, but when i select stress, the system shows a sign of stress with strikethrough...please tell me why is this happening?
thanks

[Anders Blom]

The extended Huckel models we have don't have a pair potential so the stress cannot be computed. The same is true for forces and hence you also cannot use the Huckel model to perform geometry optimizations. It is in principle possible to add a pair potential to the Huckel model though, if you have fitted one.