4.6966380876 * 8.314 = 39.048 (where, Gas constant, R = 8.314 J/(mol K) ) and for Silicon N = 2, so 3N=6 modes So, Specific heat, C_v= 38.761 / 3N = 6.5080 J/(mol K) Experimentally the Specific heat, C_v of Si at 25 ??C (~298) is found equal to 9.789 J??mol???1??K???1. Can anybody could explain the reason behind this huge error in the calculation of specific heat ? Regards Amit N.Harode CR Labs INDIA > Try to compare your calculated phonons and phonon DOS for Si first - > do they > come out as obtained e.g. by Giannozzi/De Gironcoli/Pavone/Baroni > PRB 1991 ? > nicola On Mon, 24 May 2010 18:38:31 +0530??? wrote >Dear All > > I have attempted to calculate the specific heat of Si using "F_QHA.x", and the calculated Silicon phonon dos??? as an input. > (The calculated Si phonon frequencies are in excellent agreement with available experimental data. ) > > As the output of "F_QHA.x", I have obtained the following results, (in QHA.out file) > > ############################################################################################################ > > # T in K, F_vib in Ry/cell, C_v in R (the universal gas constant by 3N modes), S in k_B > ############################################################################################################ > #??? ?????? T??? ??? ??? ??? ?????? E_internal??? ??? ??? ??? F_vibration??? ??? ??? ??? ??? Specific heat (C_v)??? ??? ??? ?????? Entropy > ############################################################################################################ > : > : > ??? 295.00??? ??? ??? 0.0139740852??? ??? ??? 0.0055747646??? ??? ??? ??? ??? ?????? 4.6621714979??? ??? ??? ??? ??? 4.4956255367 > 300.00??? ??? ??? 0.0141222695??? ??? ??? 0.0054311560??? ??? ??? ??? ??? ?????? 4.6966380876??? ??? ??? ??? ??? 4.5742737931 > 305.00??? ??? ??? 0.0142715257??? ??? ??? 0.0052850687??? ??? ??? ??? ??? ?????? 4.7298757363??? ??? ??? ??? ??? 4.6521815403 > 310.00??? ??? ??? 0.0144218157??? ??? ??? 0.0051365259??? ??? ??? ??? ??? ?????? 4.7619351485??? ??? ??? ??? ??? 4.7293532915 > : > : > : > ############################################################################################################ > >
