On Apr 10, 2010, at 10:22 , Shyam Khambholja wrote: > I have performed total energy calculation for Al as a function of > lattice parameter. > then i fit those data to murnaghan equation of state and got bulk > modulus. when i > use method of hydrostatic strain and got bulk modulus, it is much > smaller than the > one obtained by fitting E-a curve to murnaghan eos. So, which one > is more reliable, > since, bulk modulus obtained by fitting to mur. eos is quite near > to experimental data. > and which one should be used to determine other elastic stiffness > constant ?
this is one of the first thing anybody involved in calculations in solids should know. Fitting to an equation of state converges more quickly with the plane- wave basis set. If however you find large differences between the various methods, either you did something wrong, or you are very fare from convergence wrt PW P. --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
