This paper uses a molecular static approach with a many-body potential to investigate the surface energetic and bonding characteristics of tetrahexahedral platinum nanocrystals enclosed by high-index facets such as {210}, {310}, {410}, {520} and {730}. It mainly focuses on the effect of crystal size and surface Miller index on these characteristics. The results show that the surface energy and dangling bond density increase with decreasing diameter of tetrahexahedral nanocrystals and generally show an order of {210} 〉{730}〉 {520} 〉 {310} 〉 {410}. However, this order is not valid at crystal sizes below 7 nm or so. The results of corresponding surfaces are also presented for comparison.
Na-substituted dilithium orthosilicate Li2CoSiO4 was investigated by performing density functional theory calculations within the GGA+U framework. The effects of Na-substitution on the electronic structures and structural properties of Li2CoSiO4 were presented. The results show that the Na-substitution on Li sites in Li2CoSiO4 induces a lowering of the conduction bands and a narrowing of the band gap, which could be helpful for enhancing the electronic conductivity. On the other hand, the Na-substitution on the Li ions in Li2CoSiO4 leads to the expansion of interlayer space of the adjacent corrugated layers. This lattice expansion effect would benefit the Li ion diffusion.
