Effects of nonstoichiometry and ordering on the basic lattice constant of vanadium carbide VC$_y$

The effect of nonstoichiometry and ordering on the lattice constant $a_{B_1}$ of the basic lattice of vanadium carbide VC$_y$ ($0.65 < y < 0.875$) is studied. A change in the lattice constant of disordered carbide VC$_y$ at the reduction of the carbon content is considered using the direction of static displacements of atoms near a vacancy. A model for the calculation of the basic lattice constant $a_{B_1}$ of vanadium carbide is proposed taking into account nonstoichiometry and ordering. It is shown that the ordering of vanadium carbide VC$_y$ with the formation of V$_6$C$_5$ and V$_8$C$_7$ superstructures results in an increase in the basic lattice constant as compared to disordered carbide.