| Abstract: |
Hybrid simulations are widely used in material science to investigate phenomena that require both a large system size and a high level of accuracy in critical regions. The most persistent difficulty lies in bridging between models that are optimized for different length scales. Thus, hybrid atomistic simulations using a combination of classical potentials and quantum mechanics (QM) introduce undesired dangling bonds at the outer surface of the QP region. Using density functional theory (DFT) we investigate possible terminations for clusters in metallic systems where hydrogen termination is inappropriate. Aluminum slabs and clusters with different terminations (Na, Li, H and unterminated) are analyzed for several thicknesses, with and without defects. Copper clusters with different terminations (Li, Mg and unterminated) are also examined. Atomic displacements, the density of states, and vacancy formation energies are used to determine the effectiveness of the terminations. Unterminated sufraces work best for very small slabs, while, for intermediate sizes, metallic terminations are a better choice. Above a thresold size, terminated and unterminated systems behave very similarly. For clusters, the optimal choice for the termination depends upon the material and boundary condition (fixed or free shell of atoms). |
