How about trying to fit a very accurate set of data around the minimum with a parabola and calculate thus the bulk modulus? Have you tries to plot the resulting fitted curves? which one fits best the raw data? Udaygiri: in Science (as well as in Life) there is no free lunch ... Enjoy Science, no less than Life. SB
On Sep 8, 2009, at 9:04 PM, udayagiri sai babu wrote: > > hi all > i am using ev.x file given in the pw_tools directory to calculate > bulk modulus and lattice parameter values of chromium. i used > murnaghan equation of state to fit my data i got bulk modulus of 256 > gpa where as my experimental value is 160 gpa but when i used keane > equation of state to fit the same data i got 148 gpa bulk modulus > > why is this much variation? which equation of state should i use for > cr? because for vanadium and Ti murnagan euation of state has given > reasonable (<20% error) values of bulk modulus but not for Cr > > please give some suggestions > -- > U.Saibabu > PhD student, > Deformation mechanisms modeling group, > Materials engineering department, > IISc Bangalore, > India. > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20090908/a28a6cfb/attachment.htm
