thanks for quick, i just tried a quick calculation for my curiosity on this. i just optimized a fcc structure under 100GPa pressure also under 0GPa i calculated bulk modulus for 0GPa system by changing equilibrium celldm(1) in range of -10% and +10% and calculatin energy. and used ev.x for fitting. fiiting curve is an U-shaped plot
then i did the same procedure for 100GPa system by calculating energy for the celldm(1) values -10% to +10%. first thing is: alatt vs energy plot is not U-shaped. and if i extend the range from +-10% to +-20% a get an equilibrium energy but obviously it is the same as that of 0GPa's result. that is the point that i am getting confused by. and still curious about, what should i do to calculate a bulk modulus for a system under 100GPa? thank you On 02/26/2012 03:18 PM, Stefano Baroni wrote: > Why not? Bulk modulus is just the second derivative of the energy wrt volume > (modulo some appropriate definition). Don't be fooled by names. If you are > guided by concepts, rather than by names, it should be pretty clear what can > be calculated and what cannot. If it's the second derivative of the energy > wrt volume that you need, it should be obvious that it can be calculated and > how. No matter what the name is. If it is something else, well it depends ... > (on concepts, not on names). SB > > -- > Stefano Baroni, Trieste -- swift message written and sent on the go > > On 26/feb/2012, at 20:51, bahadir<bahadira at buffalo.edu> wrote: > >> hi, >> mayb this is a stupid question but i wonder if is it possible to >> calculate bulk modulus under different pressures? or is it meaningless. >> i have seen some articles that gives pressure vs. bulk modulus data. but >> it confuses me. >> >> thanks >> >> -- >> Dr.Bahadir Altintas >> >> * Dept. of Chemistry >> SUNY Buffalo >> NY,USA >> >> * Abant Izzet Baysal University >> Dept. of Computer Education >> Bolu,Turkey >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum -- Dr.Bahadir Altintas * Dept. of Chemistry SUNY Buffalo NY,USA * Abant Izzet Baysal University Dept. of Computer Education Bolu,Turkey
