Effective first-principle description of thermodynamics for BCC Nb-V system by involving the contributions of chemical order, lattice distortion and vibration.

The thermodynamic properties of body-centered cubic Nb-V system are well described using the integrated methodology of first-principle calculations, cluster expansion and Monte Carlo simulations, where the contributions from chemical order, lattice distortion and lattice vibration are included. Lattice distortion yields important influence on the phase stability of Nb-V system, while the lattice vibration leads to relatively small effect although the magnitude of vibrational entropy is large compared to the configurational entropy. In addition, lattice distortion also strongly correlates with the order-disorder transition and the degree of short-range order. By accounting for the contributions from chemical ordering, lattice distortion, and lattice vibration, the present first-principle calculations predict a miscibility gap in perfect line with the available experimental data and CALPHAD simulations. The efficient computational methodology adopted in the present work provides a transport route for the effective description of phase stability at finite temperature for complex alloys. • The thermodynamic properties of Nb-V system are effectively described. • The contribution of lattice distortion decreases the transition temperature of Nb-V. • Predicted critical temperature of the miscibility gap agrees well with experiments. [ABSTRACT FROM AUTHOR]