Dear Developers and Usres of QE. Here i am trying to compare the experimental Cv value to calculated (using phdos by ph.x,q2r.x and matdyn.x) Cv, but i am shocked that i am obtaining very large value of Cv and the sum(dos)=5.9782=3*N=3*2 in my system(AlN with 2 atoms per unit cell in fcc structure ) which is very correct. For calculation of Cv, Cv=3*R*integration( D(w)dw (hbar^2w^2/K^2T^2)*exp(x)/(1-exp(x))^2) or 3*R*integration of f(w).where x=hbar*w/K*T.
>>experimental Cv approx Cp at 300K=30.239(J/mol.K) >>therotical Cv at 300K=147.4268(J/mol.K). Sir if i will take one degree of freedom then Cv at 300K=147.4268/3=49.1422 which is also not near about 30.239(J/mol.K). I have also plot the graph between Cv/3R vs T/theta which shows good shape which is in litecture but i got y-axis starting from 0 to 5.9104. So should i calculate the phonon dos for lesser value of q point or what should i do for getting correct result. Any kind of help will be appreciable. -- Thanks and Regards Bramha Prasad Pandey GLA University, Mathura. INDIA. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120220/a7bbe120/attachment.htm
