Investigation of the influence of lattice anharmonicity on the specific heats of diamond, silicon, and germanium

The isochoric specific heats of diamond, silicon, and germanium have been calculated ab initio using the quantum-statistical method. The phonon energy has been calculated by the Morse potential. The anharmonicity of lattice atomic vibrations is shown to occur at temperatures below the Debye temperature. Experimental data on the temperature dependences of the specific heats of diamond, silicon, and germanium can be interpreted more correctly by taking into account the lattice anharmonicity.