Phase stability, mechanical property, and electronic structure of an Mg-Ca system

First principle calculations reveal that Mg-Ca phases are energetically favorable with negative heats of formation within the entire composition range, and that a strong chemical bonding is formed between Mg and Ca atoms. Calculations also show that the composition has an important effect on mechanical properties of Mg-Ca, and that the Mg-Ca phases with an Mg composition of less than 50 at.% would be good candidates as degradable bone materials in terms of Young's modulus and ductility. In addition, it is found out that Mg3Ca, MgCa and MgCa3 have phase sequences of BCC --> HCP, BCC --> HCP and FCC --> HCP under high pressure, respectively, and that Ca plays a dominant role in determining the electronic structures and stable crystal structures of various Mg-Ca phases. (C) 2011 Elsevier Ltd. All rights reserved.