Exploratory Study of Substitutional Elements in Mg₂Si for Inducing State of Negative Chemical Pressure

Abstract

First-principles calculations were used to investigate the effects of substituting a Mg atom in Mg₂Si with a foreign atom. The aim was to chemically induce a state of negative pressure for Mg₂Si, which would theoretically increase its thermoelectric power factor. First, density of states (DOS) calculations were performed for Mg₂Si with a Mg atom substituted with Group 3–12 elements (Sc to Zn). The results suggest that Group 3 and 4 elements are good candidates because the main features of the DOS curves for the substituted Mg₂Si were the same as that of the undoped semiconductor. Structural optimization and energy calculations were then performed for Mg₂Si substituted with Sc, Y, La, Ti, Z, and Hf. Only Sc and Y showed negative energy changes as a result of the substitutional reaction. The volume changes indicate that only Y is an appropriate substitutional element for inducing a state of negative pressure for Mg₂Si.