Theoretical specific heat, and thermal conductivity estimated by detailed phonon vibrations

Abstract

We report the calculation results of specific heat ($c_v$), and thermal conductivity ($\kappa$) by using Einstein, and Debye models about rock salt (NaCl), oxides: Na$_x$CoO$_2$, SrTiO$_3$, and LiNbO$_3$. In calculation, the longitudinal (L), and transverse (T) sound velocities ($v_T$, $v_L$) were estimated from acoustic phonons' dispersion's (~$\omega$/$K$) in above materials, and the average sound velocities ($v_a$) were input into Debye model for $\kappa$ equation, and results were compared with that of Einstein model. In some oxides, $v_a$ is relatively reduced at slight high $v_T$ ($v_T$/$v_L$=0.3-0.5). The relation of $\kappa$, $v_a$ and $T$ were imaged as the contour plots about realizing low $\kappa$ values to be application of thermoelectric properties.