Using the meta-generalized gradient approximation （meta-GGA） exchange correlation TPSS functional, the geo-metric structures, the relative stabilities, and the electronic properties of bimetallic AgnX （X=Au, Cu; n=...Using the meta-generalized gradient approximation （meta-GGA） exchange correlation TPSS functional, the geo-metric structures, the relative stabilities, and the electronic properties of bimetallic AgnX （X=Au, Cu; n=1-8） clusters are systematically investigated and compared with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n = 6 for the AgnAu clusters, and at n = 5 for AgnCu clusters. For different-sized AgnX clusters, one X （X=Au or Cu） atom substituted Agn＋l structure is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied molecular orbital-lowest unoccupied molecular orbital （HOMO LUMO） energy gaps show interesting odd-even oscillation behaviours, indicating that Ag2,4,6,s and Agl,3,5,7X （X=Au, Cu） clusters keep high stabilities in comparison with their neighbouring clusters. The natural population analysis reveals that the charges transfer from the Agn host to the impurity atom except for the Ag2Cu cluster. Moreover, vertical ionization potential （VIP）, vertical electronic affinity （VEA）, and chemical hardness （η） are discussed and compared in depth. The same odd even oscillations are found for the VIP and η of the AgnX （X=Au, Cu; n=1-8） clusters.展开更多
We develop a benchmark system for van der Waals interactions obtained with MP2+△CCSD(T)method at complete basis set limit.With this benchmark,we examine the widely used PBE+D3 method and recently developed SCAN+rVV10...We develop a benchmark system for van der Waals interactions obtained with MP2+△CCSD(T)method at complete basis set limit.With this benchmark,we examine the widely used PBE+D3 method and recently developed SCAN+rVV10 method for density functional theory calculations.Our benchmark is based on two molecules:glycine(or Gly,an amino acid)and uracil(or U,an RNA base).We consider six dimer configurations of the two monomers and their potential energy surfaces as a function of relative distance and rotation angle.The Gly-Gly,Gly-U,and U-U pairs represent London dispersion,hydrogen bonding,andπ–πstacking interactions,respectively.Our results show that both PBE+D3 and SCAN+rVV10 methods can yield accuracy better than 1 kcal/mol,except for the cases when the distance between the two monomers is significantly smaller than the equilibrium distance.In such a case,neither of these methods can yield uniformly accurate results for all the configurations.In addition,it is found that the SCAN and SCAN+rVV10 methods can reproduce some subtle features in a rotational potential energy curve,while the PBE,PBE+D3,and the local density approximation fail.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10774103 and 10974138)
文摘Using the meta-generalized gradient approximation （meta-GGA） exchange correlation TPSS functional, the geo-metric structures, the relative stabilities, and the electronic properties of bimetallic AgnX （X=Au, Cu; n=1-8） clusters are systematically investigated and compared with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n = 6 for the AgnAu clusters, and at n = 5 for AgnCu clusters. For different-sized AgnX clusters, one X （X=Au or Cu） atom substituted Agn＋l structure is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied molecular orbital-lowest unoccupied molecular orbital （HOMO LUMO） energy gaps show interesting odd-even oscillation behaviours, indicating that Ag2,4,6,s and Agl,3,5,7X （X=Au, Cu） clusters keep high stabilities in comparison with their neighbouring clusters. The natural population analysis reveals that the charges transfer from the Agn host to the impurity atom except for the Ag2Cu cluster. Moreover, vertical ionization potential （VIP）, vertical electronic affinity （VEA）, and chemical hardness （η） are discussed and compared in depth. The same odd even oscillations are found for the VIP and η of the AgnX （X=Au, Cu; n=1-8） clusters.
基金supported by US National Science Foundation under Grant No. DMREF-1627028
文摘We develop a benchmark system for van der Waals interactions obtained with MP2+△CCSD(T)method at complete basis set limit.With this benchmark,we examine the widely used PBE+D3 method and recently developed SCAN+rVV10 method for density functional theory calculations.Our benchmark is based on two molecules:glycine(or Gly,an amino acid)and uracil(or U,an RNA base).We consider six dimer configurations of the two monomers and their potential energy surfaces as a function of relative distance and rotation angle.The Gly-Gly,Gly-U,and U-U pairs represent London dispersion,hydrogen bonding,andπ–πstacking interactions,respectively.Our results show that both PBE+D3 and SCAN+rVV10 methods can yield accuracy better than 1 kcal/mol,except for the cases when the distance between the two monomers is significantly smaller than the equilibrium distance.In such a case,neither of these methods can yield uniformly accurate results for all the configurations.In addition,it is found that the SCAN and SCAN+rVV10 methods can reproduce some subtle features in a rotational potential energy curve,while the PBE,PBE+D3,and the local density approximation fail.
