Effects of Alloying Elements M (M = Fe, Mo) on Phase Stability of Cr_(23)C_6 Carbides from First-principles

摘要

The structural and electronic properties of (Cr, M)_(23)C_6 (M = Fe, Mo) with a full composition range of Cr/M ratio were carried out by first-principles calculations. The phase stability was investigated by calculating the reaction energy. Results reveal that Cr_(22)FeC_6, Cr_(21)Fe_2C_6, Cr_(20)Fe_3C_6, Cr_(21)Mo_2C_6 and Cr_(20)Mo_3C_6 are the stable phases. Alloying element Fe and Mo prefer to occupy the 4a and 8c sites of Cr_(23)C_6 carbides, respectively. Then the stabilized mechanism by alloying elements in Cr_(23)C_6 carbides was explored by employing the charge density difference. It provides the explanation that the high stability of Cr_(22)FeC_6 and Cr_(21)Mo_2C_6 is mainly attributed to the strengthening of covalent bonds between the 8c and 32f sites.