Ab initio thermodynamic properties of certain compounds in Nd-Fe-B system.

• Ab initio calculation of formation enthalpy of Nd-Fe-B compounds with GGA + U method. • Phonon calculation of compounds to obtain heat capacity for 300 < T < 3000 K. • Re-optimization of binary Nd-B phase diagram using ab initio calculation results. • Improvement especially from results for NdB 6 compound. In this work, we report the results of ab initio calculations of thermochemical properties of several compounds in the Fe-Nd, B-Nd and B-Fe-Nd systems. We have performed DFT + U calculations to compute the enthalpy of formation of the compounds NdB 6 , NdB 4 , Nd 2 B 5 , Nd 2 Fe 17 and Nd 5 Fe 2 B 6 . It was found that the values obtained with an effective Hubbard U correction have better agreement with the experimental data. We have also computed the vibrational contribution to the heat capacity ( C p ) of the compounds as a function of temperature was computed using the quasiharmonic approximation. For most of the compounds these properties have not been experimentally determined until now. Electronic contribution to the heat capacity has been calculated as well from electronic structure calculations. A part of the results in this work has been applied to the re-optimization of the binary Nd-B phase diagram. [ABSTRACT FROM AUTHOR]