Interesting physics. Thermal expansion.

Thermal expansion. An increase in temperature leads to an increase in the average distance between atoms. The amplitude of thermal vibrations of atoms in the crystal lattice increases. Atoms in the crystal lattice make anharmonic (i.e., non-harmonic) oscillations. This is due to the nature of the dependence of the forces of interaction between atoms on the distance between them .When the amplitude of vibrations of atoms increases due to heating of the crystal, the growth of repulsive forces between atoms pr