The Crystal is considered as a quasi-equilibrium distribution of molecules moving in the proximities of lattice points, while the interchange of molecules between the lattice cells is neglected. The approximate equation for the one-particle probability density function is derived from the LIOUVILLE equation. The nonperiodic solutions of this equation are investigated. Such solutions correspond to the fact that in the crystal each molecule belongs to the proximity of one lattice point. The rule for construction of thermodynamic functions is developed. The equilibrium condition is analyzed. The case of collective vibrations is considered in a harmonic approximation.