# Thermal and mechanical properties of Ni-Cr alloys with ReaxFF

Understanding the temperature-dependent mechanical strength and physical properties such as elastic constants and the thermal response is essential for the applications of metallic alloys. While ReaxFF force fields for transition metals have been successfully applied to studying various materials, it has been found that reproducing the experimental elastic constant, C44 is challenging. The previously developed ReaxFF force fields for transition metals, including fcc Ni and bcc Cr, did not include the three-body interaction parameter set, which may be essential for giving the directionality of the bonds between three neighboring metal atoms.

In a recent study, three-body interactions such as Ni-Ni-Ni and Cr- Cr-Cr valence angle parameter sets for the Ni- and Cr-metal, and Ni-Cr- Cr, Cr-Ni-Cr, Ni-Ni-Cr and Ni-Cr-Ni angles for the Ni/Cr alloy were introduced to the ReaxFF transition metal description. It is shown that the inclusion of three-body interaction terms allows ReaxFF to achieve a higher accuracy for predicting mechanical and thermal properties of transition metals – ReaxFF can successfully predict (1) the temperature-dependent elastic constants, bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio at finite temperatures, (2) the thermal lattice expansion and (3) the melting temperature and the material properties near the melting temperature of Ni and Cr transition metals. A recent paper shows that three-body interaction terms in a ReaxFF force field strongly improve the description of mechanical and thermal properties of transition metals and their alloys. The high-temperature properties of materials are described more accurately with the new ReaxFF force field, which is crucial for the modeling and designing of the desired alloys.

Yun Kyung Shin, Yawei Gao, Dongwon Shin, Adri C.T. van Duin, Impact of three-body interactions in a ReaxFF force field for Ni and Cr transition metals and their alloys on the prediction of thermal and mechanical properties, Computational Materials Science (2021), 197, 110602.

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