Parameters setup for first-principles on well-formedness and thermodynamic properties of bulk and habit surfaces of Mg2Si

Abstract

The well-formedness, thermodynamic properties and mechanical properties of Mg _2 Si bulk and Mg _2 Si (1 0 0), (1 1 0) and (1 1 1) surfaces were calculated by using first-principles based on density functional theory (DFT). Some accurate and efficient parameters were programed by computing massively and repeatedly. The accurate and efficient parameters used in Mg _2 Si bulk is Energy cutoff (500 eV), k-point (5 × 5 × 5) and exchange-correlation interaction (PBEsol). The relaxation of surficial atoms shows that the rule or rate of expansion and shrink are similar from the second column. The rate of the innermost layer decreases gradually with increasing slab thickness. The rate of the innermost layer in Mg-terminated or Si-terminated Mg _2 Si (1 0 0) and (1 1 0) is no more than 0.1% when convergent layers are no less than 11. The convergent layers of Mg ^2 -terminated and Si-terminated Mg _2 Si (1 1 1) are 14 and 16, respectively. The Mg ^1 -terminated Mg _2 Si (1 1 1) surfaces hardly converge even if the layers reach to 18. Si-terminated surfaces are harder to keep stability than Mg-terminated surfaces in Mg _2 Si (1 0 0) and (1 1 1) surfaces because of a higher surface energy. Mg _2 Si (1 1 0) surface energy is a constant because of the nonpolar and stoichiometric Mg-Si terminated surface. Si-terminated and Mg-terminated Mg _2 Si (1 0 0) surfaces are more stable than Si-terminated and Mg ^2 -terminated Mg _2 Si (1 1 1) surfaces, respectively. Mg ^1 -terminated Mg _2 Si (1 1 1) surface is the most stable surface over the entire surfaces in Mg _2 Si.

Keywords

• habit surfaces
• surface relaxation
• surface energy
• first-principles