Influence of Defect Dynamics on Lattice Distortion and Mechanical Behavior in High Entropy Carbides (HECs) Using First Principles Study

High Entropy Carbides (HECs) are made up of compositions of disordered refractory five metal carbides in a rocksalt structure containing different combinations of the elements Hf, Nb, Mo, Ta, Ti, V, W, and Zr. Investigating the role of lattice distortion is key to unlocking HECs' full potential. Distortion of the crystal lattice occurs due to the introduction of impurities, such as vacancies and interstitials, which impact the structural and mechanical properties of HECs. This research uses Density Functional Theory (DFT) calculations to study how carbon vacancy point defects affect the lattice distortion of the HECs and their respective Transition Metal Carbides (TMCs). Primarily, we explored the bulk modulus of HECs with a carbon vacancy and found that the bulk modulus was lower with the added defect. We also analyzed to what extent the properties of the HECs can be predicted based on their respective TMCs. The bulk modulus was moderately predictable using TMCs. To better understand the behavior of the bulk modulus, we explored the bond lengths of the metal and carbon pairs in each HEC with presence of the carbon vacancy. The bond lengths of HECs with this vacancy are relatively predictable from the averaged bond lengths of TMCs, except for HEC16. HEC3 was the most predictable. We also found that VC and TiC are the least predictable from their TMCs. Based on the current results, we will delve into the interpretation of the Radial Distribution Functions (RDF), Density of State (DOS), and Bader charges, to gain insight into how the carbon point defects influence the lattice distortion by understanding each metal element's behavior. We will extend this research to a variety of point defects, such as interstitial and anti-site defects, to develop a more comprehensive understanding of defect mechanisms.