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The purpose of this work is to study the region of existence of the sigma phase of the Fe-V system. The original algorithm for finding the minimum total energy was developed and tested depending on two independent variables. The optimized values of the lattice parameters for the σ-phase alloys of the Fe-V system are calculated. Dependence of the mixing energy of the σ - phase as a function of the composition x (V) of the sigma - phase of the Fe-V system was obtained. The calculations were carried out using the license package of quantum-mechanical calculations WIEN2k.

The purpose of this work is to study the region of existence of the sigma phase of the Fe-V system. Since this phase is stable up to low temperatures, up to temperature of the ground state, at which quantum-mechanical calculations are carried out. This one allows testing quantum-mechanical calculations for sigma – phase Fe-V alloys. The original algorithm for calculating the minimum total energy was developed and tested depending on two independent variables [1, 2, 3]. The optimized values of the lattice parameters for the σ-phase alloys of the Fe-V system are calculated. Dependence of the mixing energy of the σ – phase as a function of the composition x (V) of the sigma - phase of the Fe-V system was obtained. The calculations were carried out using the license package of quantum-mechanical calculations WIEN2k.

The region of existence of the sigma-phase of the Fe-V system was studied. The calculations carried out using the licensed package of quantum mechanical calculations WIEN2k. The dependences of the mixing energy and partial magnetic moments of Fe atoms in alloys of the Fe-V system, located on different sublattices depending on the composition, was obtained.

The three-sub-lattice approximation model calculations of the energies and magnetic parameters (Curie temperature and mean magnetic moment) were used. The distributions of atomic species between different model sub-lattices and the thermodynamic properties depending on the Fe-V alloy compositions at T = 0K were evaluated by solving the set of equations at T = 0K obtained by minimizing the functional ΔG with respect to the independent configuration degrees of freedom.The comparison of the calculated data on the structural properties of -phases in Fe-(Cr, V) systems depending on composition and temperature was conducted.The consistency of the input data and the calculation results for the thermodynamic properties is obtained, namely, the dependence of the enthalpy of mixing of the -phase of the Fe-V system on the composition relatively of the BCC phases of pure Fe and V. The input data was used to find the initial values of the model parameters.The consistency of these data proves the correctness of the found energy parameters of the model.