Temperature Dependence of the Entropy and the Heat Capacity Calculated from the Raman Frequency Shifts for Solid Benzene, Naphthalene and Anthracene

Authors : Hamit YURTSEVEN, Hilal ÖZDEMİR

Pages : 55-62

Doi:10.5541/ijot.1108782

View : 8 | Download : 3

Publication Date : 2022-09-01

Article Type : Research Paper

Abstract :Temperature dependences of the free energy insert ignore into journalissuearticles values(F);, entropy insert ignore into journalissuearticles values(S); and the heat capacity insert ignore into journalissuearticles values(C_v); are calculated insert ignore into journalissuearticles values(P=0); for the organic compounds insert ignore into journalissuearticles values(solid benzene, naphthalene and anthracene); by using the quasiharmonic approximation. Contributions to those thermodynamic functions due to the Raman frequencies of lattice modes insert ignore into journalissuearticles values(solid benzene);, librational modes insert ignore into journalissuearticles values(naphthalene);, phonons and vibrons insert ignore into journalissuearticles values(anthracene); are taken into account in our calculations. We obtain that similar linear increase of F and nonlinear increase of S and C_v, occur with the increasing temperature in benzene and naphthalene. This linear insert ignore into journalissuearticles values(F); and nonlinear insert ignore into journalissuearticles values(S, C_v); increase is rather different for anthracene as the molecular structure becomes complex insert ignore into journalissuearticles values(benzene-naphthalene-anthracene);, as expected. Our calculations by the quasiharmonic approximation can be compared with the experiments for those organic compounds.
Keywords : Quasiharmonic approach, Free energy, Entropy, Heat capacity