Thermal properties were calculated using the first principles methods. First principle theory is also called ab
initio theory. It calculates material behaviours without definition of any material properties. The calculation is
based on the Schrödinger’s equation with appropriate assumptions. Calculations of thermal properties were
conducted using two ab initio software packages [4, 17-19].
All the calculations were based on solving the Schrödinger’s equation at ground state (temperature is 0 K). The
total energy of the ground state is uniquely determined by the electron density described by the following equation