Aron Walsh, Richard Catlow, Alexey Sokol and Scott Woodley Materials Chemistry, Department of Chemistry, University College London Global and Local Minimum Structures for Clusters of Indium Sesquioxide
Goal and Methods • Derive robust interatomic In2 O3 potential. Explore high pressure behaviour. • Determine lowest energy structures formed from stoichiometric building blocks: (In2 O3 )n n = 1 – 7 Global optimization: Evolutionary algorithm (GULP). • Validate and characterize using a first-principles method. Density functional theory calculations (VASP). • Assess structural trends, stability and optoelectronic properties.
Interatomic Potential: In2 O3 6 exp i j ij ij ij ij q q r C U A r r ρ ⎛ ⎞ = + − − ⎜ ⎟ ⎝ ⎠ Property Experiment Literature Potential1 Sokol Potential2 LDA-DFT a (Å) 10.117 10.120 10.121 10.094 B (GPa) 194.24 222.79 193.77 174 ε0 8.9-9.5 6.87 9.05 ε∞ 4.0 3.53 3.90 3.82 • Buckingham potential with shell polarization on oxygen. 1O. Warschkow et al., J. Am. Ceram. Soc. 86, 1700 (2003). 2A. Walsh et al, Chemistry of Materials 21, 4962 (2009).
Conclusion • Presented a new In2 O3 interatomic potential that describes bulk and cluster properties. • n < 4 clusters have distinct symmetric global minima. • n > 4 clusters tend towards bulk-like, low symmetry particles. • Open framework clusters have high energetic cost. • HOMO and LUMO character is consistent with bulk. Future work: • Extend to higher n. • Explore excited state properties. Acknowledgements: Materials Chemistry Consortium (Access to Hector); EU FP7 (Marie Curie Fellowship).