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Embedded Cluster Model for Al2O3 and AlPO4 Surfaces Using Point Charges and Periodic Electrostatic Potential

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journal contribution
posted on 21.08.2017, 00:00 by Masafuyu Matsui, Shigeyoshi Sakaki
An embedded cluster model with either a large number of point charges (PCs) or periodic electrostatic (PE) potential was proposed to incorporate the electrostatic effects by the bulk surface and applied to non-transition-metal oxide supports such as Al2O3 and AlPO4. A large number of PCs are placed on several layers of surface. The PC values were taken to be the same as the Bader charges obtained from periodic DFT calculation of slab model. The PE potential was derived so as to consider the infinite three-dimensional PC distribution obtained by the calculation of slab model. One electron integral of the PE potential in the Gaussian basis function was evaluated using Poisson’s equation, Fourier transformation within a supercell approach, and the Ewald summation method. These embedded cluster models were applied to Rh2-adsorbed Al2O3 and AlPO4. A bare cluster model with neither PC nor the PE potential presented very poor computational results for the interaction energies of Rh2 with Al2O3 and AlPO4 surfaces, density of states, projected density of states, frontier orbital features, and spin density distribution. In contrast, the embedded cluster model successfully reproduced those properties when either a large number of PCs or the PE potential was employed. These results indicate that the embedded cluster models proposed here are useful for investigating theoretically non-transition-metal oxide surface using the hybrid DFT functional.