DFT simulations of the distribution of Fe and O atoms in BCC (β) and HCP (α) phases of α–β Ti–O–Fe alloys. (IMAGE)
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a, A DFT BCC (1¯12¯1¯12¯)/HCP (1¯1001¯100) interface model containing one octahedral interstitial O atom (in red) and one substitutional Fe atom (in green) at their respective favourable positions. On the basis of Fig. 3, we constructed a 1 × 1 in-plane ten-layer BCC (1¯12¯1¯12¯)/1 × 2 in-plane ten-layer HCP (1¯1001¯100) interface structure (ten layers on each side) to simulate an α/β interface. The red arrows indicate the equivalent BCC/HCP interfaces owing to the periodic boundary conditions. b,c, The calculated layer-resolved relative energy mapping for an interstitial O atom (b) and a substitutional Fe atom (c) throughout the interfaces. The relative energy as a function of pair separation for O and Fe in each phase was also calculated. d,e, The calculated relative total energy as a function of pair separation for pair interstitial O atoms in a 96-atom HCP-Ti supercell (d) and pair substitutional Fe atoms in a 54-atom BCC-Ti supercell (e). The calculated equilibrium O and Fe concentrations were based on the respective energetically most favourable configurations (see text).
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