Hi all,

I just started learning the lammps and it seems really to be powerful tool, unfortunatly i dont know how to use it in the way that i need it. anyway, i want to determin the elastic constant of a the cooper, i am using eam potential. i know that we can determin this for 0k temperature but i need to vary the temperature while the pressure is constant and then to vary the pressure while holding the temperature constant, which means that i have to pass through all the control stuff. Honestly i have no clue and i dont really get it from the main website, so i need an example to understant. if someone have done this before, it will be great if you can share it. or put me in the right way, where to look for examples.

thanks

Look at examples/ELASTIC which has an example of it.

Steve

Aidan may have additional comments - he's done this before.

Steve

There is no simple way to compute elastic constants for T>0. One thing you

can do is mimic the examples/elastic calc, but replacing the single pressure

evaluation with the average pressure from an equilibrated NVT simulation.

All the formulas translate.

Aidan

Hi, Raouf. J. R. Ray wrote several papers on this topic (calculating elastic consts. using MD sims) in the 1980s - some with Rahman, some with others, some by himself. They contain fluctuation formulas and nice clear discussions - particularly in his long review article (I forget the journal-ref). Not sure if this material has passed conveniently into a textbook, but you can always download the original papers.

Best,

Rob