Haishun Wu

GEOMETRY OPTIMIZATION OF CN (N =2?30) WITH GENETIC ALGORITHM

Abstract The geometries of C n (n=2–30) clusters have been optimized with a genetic algorithm (GA) associated with simulated annealing (SA) method on the Brenner bond-order potential energy surface (PES). It showed that the geometries are linear when n is less than 6, single ring when n is at 6–12, double ring when n is equal to 13 or 14. Multi-ring structures start as n is greater than 14. C 28 is in a fullerene structure; while C 20 and C 21 are bowl- and cap-like, respectively. The other multi-ring structures were predicted to be planar. Further analysis indicated the stability of the non-planar open structures on the Brenner PES is related to the number of the triple bonds in the clusters.

Ab initio calculation of SiC polytypes

Abstract A systematic study of ground-state property of cubic and hexagonal silicon carbide polytypes (3C-, 6H-, 4H-, and 2H–SiC) is reported using the ultrasoft and norm-conserving pseudopotential methods of density-functional theory in the local-density approximation. The electronic and geometry structures of SiC polytypes are discussed in comparison with the experimental data. The conduction-band minimum with ultrasoft pseudopotential is the closest to (0.0,0.5,0.0) point as energy band calculation with several pseudopotentials. There is a marked discontinuity along ML line in the Brillouin zone with norm-conserving pseudopotential proposed by Lin. Both energy gap and valence-band width for the structure optimized with ultrasoft pseudopotential are greater than that with Lin’s. pseudopotential.

Structure and stability of SinCm−n clusters

Abstract In this paper, both ab initio and density functional theory methods have been used to predict geometries, electronic states and energies of Si n C m − n ( n =1,2; m =3–16). Harmonic frequencies for these clusters are given in order to aid in the characterization of the ground states. These results show that SiC m −1 ( m =3–9) clusters form linear structure and SiC m −1 ( m =10–16) isomers form ring structure. Si 2 C m −2 ( m =4–16) clusters have linear structure except ring isomer of Si 2 C 12 molecule. Si atom favor to bond at end in linear isomers. However, C atom themselves favor to bond in the cyclic isomers. The stability of the Si n C m − n ( n =1,2; m =3–16) clusters with odd m are greater than that with even m .

First principles studies on the structures, electronic states and stability of SinCm+ cationic clusters

Abstract Geometries, electronic states and energies of Si n C + and Si n C 2 + ( n =1–7) have been investigated using the density functional theory. Structural optimization and frequency analyses are performed with the basis set of 6-311G(d). The calculations predict the existence of a number of previously unknown isomers. The strong C–C bonds are favored over C–Si bonds in the Si n C 2 + cationic species. The Si 3 C + , Si 5 C + , Si 2 C 2 + and Si 3 C 2 + are more stable in the Si n C + and Si n C 2 + ( n =1–7) cationic isomers.

Structures and stability of (HAlNH n (n=1–15)

The geometries, electronic states, vibrational spectra and thermodynamic properties for (HAINH)n clusters withn=1–15 have been investigated using theab initio DFT/B3LYP method with basis sets 6-31G* and their ground state structures obtained. Comparison of the (HAlNH)n with (AlN)n clusters shows that the skeletons of (HAlNH)n consist of four-membered and six-membered rings made of Al-N bonds, and either Al or N atom forms four bonds in which three ones are Al-N bonds and the rest is Al-H or N-H bond. The number of Al-N bonds of (HAlNH)n is equal to that of (AlN)n. The magic number regularity of (HAlNH)n isn=2, 4, 6, 8, etc., all of which are even numbers.

Ab initio molecular orbital study of structure on aluminium borides A1Bn(n=1-5) series

RECENTLY, great attention has been paid to the physical and chemical properties of atomic andsemiconductor clusters. On the properties of AlB n atomic cluster, experimental studieshave been reported, yet theoretical studies have not been seen.Aluminium borides (AlB n ) have been widely used to change the fiber strength in mechanical engineering and to adjust the...