A TS Search for Stable Configurations of Double Icosahedral Ag-n (n=19, 23, 24, 25) Clusters Linked by Sharing Atoms

作者：Jiang Yuanqi^*; Peng Ping; Wen Dadong; Han Shaochang

来源：Acta Chimica Sinica, 2013, 71(10): 1429-1434.

DOI：10.6023/A13050470

• Ag-n cluster
• stable configuration
• TS search
• DMol(3)

A DMol(3) molecular orbital package based on DFT theory is adopted to calculate the energetics and electronic structures of icosahedral Agn and double icosahedral Ag (n=19, 23, 24, 25) clusters. Ab initio MD simulation for Agn cluster at 300 K is also carried out in the micro-canonical ensemble (NVE). During optimization and total energy calculation, electronic exchange-correlation energy functions represented in reciprocal space with the PBE type under GGA approximation are used. A double-numerical basis set together with d-polarization functions (DNP) is chosen to describe the electronic wave functions of Ag atoms. And only core electrons described by the DFT Semi-core Pseudopots (DSPP) are calculated. All atomic positions in Agn (n=13, 19, 23, 24, 25) clusters are relaxed by geometry optimization under RMS force of 0.002 Ha/A and RMS displacement of 0.005 A. The calculation of total energy and electronic structure is followed by the geometry optimization with self-consistent field (SCF) tolerance of 1 X 10(-5) Ha. Further, using linear synchronous transit (LST) and quadratic synchronous transit (QST) methods based on the minimum energy path (MEP) with the aid of the climbing image nudged elastic band (NEB) method, a new transition state (TS) search technique for stable configurations of clusters is developed, in which the stable configuration is independent on selected initial configurations. As this technique being applied to search the stable configurations of Ag (n=7, 13, 19, 23, 25) clusters, it is confirmed the low energy stable configuration of the isolated icosahedron Agn-Ih is indeed a plate-shape layered structure Ag-13-C-2 including a pentagonal bipyramid segment. The ground state of the double icosahedra linked with intercross sharing atoms Ag-19-D(5)h is also demonstrated to be a spherical geometry Ag-19-C-1 consisting of 6 atoms around a deformed Agn icosahedron. And similarly to Ag (n=17-22) clusters, all stable configurations of Ag-23-D(3)h, Ag-24-D(2)h, Ag-25-D-5 d clusters have a deformed Ago icosahedral nucleus as reported in literatures.

• 出版日期2013-10-15
• 单位湖南大学