M.D. Chen

A theoretical study for the isomers of neutral, cationic and anionic phosphorus clusters P5, P7, P9

Abstract The cations and anions of P 5 , P 7 and P 9 exhibit intensities of significance on the mass spectra of phosphorus clusters produced in direct laser vaporization. We have acquired in the total fifty isomers of P 5 , P 7 , P 9 and their cations and anions by means of the B3LYP, DFT method. According to total energies, the most stable isomers have been predicted. A cationic cluster prefers to adopt structures with an atom(s) which is four-fold coordinated. The planar pentagon structure is a frequent sub-unit in the phosphorus clusters. Both tetrahedral P 4 and cuneane P 8 are common components of the clusters and can be considered as important units for the construction of large clusters.

Structure prediction of large cationic phosphorus clusters

Abstract Guided by the mass spectrum of cationic phosphorus clusters produced in direct laser vaporization, we optimized nine P8 isomers with density functional calculations and chose the most stable cuneane P8 as building units for larger clusters. Eight isomers of P25+ were proposed and full geometry optimizations were carried out with molecular mechanics, semi-empirical PM3 and density functional calculations. Then four models of P33+ were built based on the most stable P25+ and P8 isomers. Other cationic phosphorus clusters up to P89+ were also constructed. In these clusters, cuneane P8 polymerizes to a long tubular shape with one extra phosphorus atom located at the end.

A density functional study for the isomers of anionic sulfur clusters S-n(-) (n=3-20)

Abstract The signals of anionic sulfur clusters are intense in the mass spectrum of sulfur clusters generated in direct laser vaporization. We have acquired numerous isomers of sulfur clusters by means of the B3LYP DFT method. According to total energies, the most stable Sn− (n=3–13) isomers are predicted. The helical Sn (n=14–20) structures are also calculated. Most of the anionic clusters are with chain configurations; the ring clusters with threefold atom(s) are higher in total energy. The most stable forms of isomers, from S9− to S13−, show helical configurations that are completely different from those of the corresponding neutral and cationic clusters.

Geometric structures and structural stabilities of neutral sulfur clusters

Abstract We have acquired a total of 68 isomers of sulfur clusters S n ( n =3–11) based on molecular graphics and then carried out optimizations and vibrational analysis by means of the B3LYP DFT method. Inside these structures, the sulfur atoms could be in one-fold, two-fold and/or three-fold coordination. According to total energies, the isomers have been ranked for stability. Many sulfur clusters are composed of atoms in two-fold mode. Compared to a S n structure with all atoms in two-fold mode, that with atom(s) in one-fold and three-fold coordinations is higher in energy. It seems that it is difficult for a sulfur cluster to form a cage structure with the involvement of three-fold atom(s)

A density functional study of CO2 adsorption on the (100) face of Cu(9,4,1) cluster model

The adsorption modes of inert CO2 on the (100) face of Cu(9,4,1) cluster model have been studies by the Slater DFT code of the Amsterdam density functional (ADF) program. The side-on adsorption mode with near linear CO2 lying at the short bridge site has the highest binding energy of 26.31 kJ mol−1. The binding energies of CO2 in similar geometry on the cross bridge, hollow, and on-top sites vary from 19.66 to 21.8 kJ mol−1. The investigation also revealed that a number of CO2 bent modes with O-C-O angles equal to ≈ 150° can coordinate with the surface with binding energies ranging from 9.66 to 23.56 kJ mol−1. Further calculations indicated that to cause the CO2 molecule to bend to ≈ 150°, there is negative 9.66 to 23.56 kJ mol−1. Further calculations indicated that to cause the CO2 molecule to bend to ≈ 150°, there is negative charge transferred from the copper cluster to the CO2 molecule.

A density functional study for the isomers of cationic sulfur clusters

Abstract The cations of sulfur clusters exhibit intensities of significance on the mass spectra of sulfur clusters generated in direct laser vaporization. We have acquired numerous isomers of cationic sulfur clusters by means of the B3LYP DFT method. According to total energies, the most stable S n + ( n =3–13) isomers are predicted. Many cationic clusters are composed of two-fold atoms; those with one-fold and three-fold atoms are higher in total energy. The most stable isomer of some cationic clusters shows a structure completely different from that of the corresponding neutral cluster.

THE PREDICTION OF ISOMERS FOR THE PHOSPHORUS CLUSTERS P7

In the study of cationic phosphorus cluster produced in direct laser vaporization, it has been observed P7· shows the highest intensity in the mass spectrum. We acquired twenty-four P7· isomers with molecular graphics and then carried out optimizations with molecular mechanics, PM3 semi-empirical and ADF density functional calculations. In these isomers, the phosphorus atoms could be in two-fold, three-fold, four-fold or six-fold coordination. P7 which derived from the most stable Ρβ by adding a phosphorus atom against the double bond has the lowest bonding energy. When there is a six-fold atom in the structure, the d orbital is involved in bonding. According to the bonding energies, the models with a planar ring or a six-fold atom are relatively less stable.