原子团簇P_(13)结构的密度泛函研究

使用分子建模软件设计出多种可能的P13团簇结构后,再用B3LYP密度泛函方法(6 31G 基组)进行几何优化和振动频率计算,得到了15种势能面上局域最小点结构(所有的振动频率均为正值),它们分别具有Cs和C2v对称性,原子团簇中的磷原子采用二或三配位成键.由楔状P8派生出的结构(Cs对称性)是最稳定的同分异体.从分子结构的几何形状上看,P8的楔状构型经常包含在P13的模型中,它是组成大分子磷原子的重要结构基元,可用来构造能量相对较低的大分子磷原子团簇

硫原子团簇负离子的螺旋结构

在使用B3LYP密度泛函进行几何构型优化和振动频率计算得到的硫原子团簇负离子的结构中,分子的总能量最低的S9- 到 S13-的同分异构体呈螺旋状构型。另外也计算了螺旋状的Sn- (n = 14~20)的结构。大多数的的硫负离子是链状结构,这与相应中性硫原子团簇的环状构型完全不同

3D Molecular Simulation on the Web

[中文文摘]绍几种基于Web上的三维分子结构模拟技术:VRML及Chime、Chem3D、HyperChem插件,并讨论它们的优缺点.这些模拟技术具有可操作的特点,可以进行旋转、缩放、平移等实时交互操作,并改变其形状和颜色的表现形式.三维分子结构模拟可以增强化学网络课程的表现能力,提高教学效果,是发展远程教育的重要技术.[英文文摘]Several techniques of 3D molecular simulation based on Web page were introduced, which are VRML, Chime, Chem3D and HyperChem plugins. Their advantages and shortcomings were also discussed.The rotations, zooms, transformations can be operated interactively, and several color and display modes are also available. 3D molecular simulations can improve performances of chemical network courses and enhance educational effects. They are important techniques on developing the long distance educations

A Density Functional Study for the Isomers of Germanium Clusters Ge_11

[中文文摘]用分子图形软件设计出多种Ge_11原子团簇模型,使用B3LYP密度泛函方法进行几何构型优化和振动频率计算,比较了14种同分异构体的总能量,得到了新的基态构型。锗原子团簇的大部分原子以三、四、五和六配位成键。在Ge11原子团簇中,双角反四棱柱衍生出来的构型能量较低,它是设计大分子锗原子团簇初始模型的重要结构单元。由三棱柱演变的构型能量居中。带心结构和共边构型带有高配位原子,其总能量较高,是不稳定的结构。[英文文摘]Fourteen models of germanium clusters Ge11 have been designed by using molecular graphics software, and the geometry optimization and calculation on vibrational frequency been carried out by means of B3LYP density functional method. Most of the germanium atoms can be in three-, four-, five- and six-fold. According to the total energies, the most stable Ge11 isomer has been predicted. The structures derived from bicapped square antiprism in configuration are lower in total energy, while those from triangle prism are less stable. The structures containing center atom or shared edge are higher in total energy and unstable.福建省科技计划重大基金项目(项目编号2002F010

Structural Stabilities of Small Cationic Sulfur Clusters

[中文文摘]用分子图形软件设计出 4 9种硫原子团簇Sn+ (n =3～ 13)的结构 ,使用B3LYP密度泛函进行几何构型优化和振动频率计算 ,根据分子的总能量得出最稳定的同分异构体 .在硫原子团簇正离子中 ,大部分原子为二配位成键 .带有一、三配位的原子结构的总能量较高 .部分最稳定硫原子团簇正离子的构型与最稳定的中性硫原子团簇的构型完全不同.[英文文摘]The cations of sulfur clusters exhibit intensities of significance on the mass spectra of sulfur clusters generated in direct laser vaporization. To our knowledge, theoretical investigations on cationic sulfur clusters are rare. Forty-nine isomers of sulfur clusters were acquired by means of the molecular model design, molecular mechanics and semi-empirical PM3 and the recently proposed and widely used B3LYP hybrid, non-local, DFT method with basis set 6-31G*. To look for stable configurations, full geometry optimizations at the 6231G3 level for all sulfur atoms were performed using Gaus2 sian 98 program packages. The initial models were constructed by means of breaking bond(s) , making bond(s) , adding atom(s) , deleting atom(s) , rotating fragment (s) , translating fragment (s) and merging fragment (s) . The one2fold , two2 fold and three2fold modes for modeling were considered , according to the bonding characteristics of the sulfur atom. Fi2 nally a total of eleven structures for S3 + , S4+ and S5+ ; ten isomers of S6 + and S7+ ; fifteen isomers of S8 + and S9+ and thirteen isomers of S10 + , S11+ , S12+ and S13 + are acquired , respectively. A large number of structural possibilities of non2minimum structures were not covered. According to total energies , the most stable Sn + ( n = 3～13) isomers are pre2 dicted. The geometry , relative stability and structural rules of these cationic sulfur clusters were described. Some struc2 tures of neutral sulfur clusters with true minima transform upon ionization into non2minimum cationic structures and vice versa. The results of a large amount of calculations show that the two2fold coordination is generally favored in sulfur cationic clusters , though some sulfur atoms coordinated with the others in one2fold or three2fold mode are higher in total energy. The most stable isomer of some cationic clusters shows a structure completely different from that of the corre2 sponding neutral cluster. In chain structures , the atoms at the two ends adopt the one2fold mode and the others are in two2fold mode. Theoretical studies on sulfur cationic structures with a three2fold atom are rare. It is unlikely to have a sulfur cationic cluster in cage structure , for the bondings of a three2fold atom are not strong enough. The calculation results can serve as guiding factors for future theoretical studies on large sulfur clusters.国家自然科学基金资助项目 (2 95 73117); 优秀国家重点实验室研究基金 (20023001

Structural stabilities of small cationic sulfur clusters

The cations of sulfur clusters exhibit intensities of significance on the mass spectra of sulfur clusters generated in direct laser vaporization. To our knowledge, theoretical investigations on cationic sulfur clusters are rare. Forty-nine isomers of sulfur clusters were acquired by means of the molecular model design, molecular mechanics and semi-empirical PM3 and the recently proposed and widely used B3LYP hybrid, non-local, DFT method with basis set 6-31G *. To look for stable configurations, full geometry optimizations at the 6-31G * level for all sulfur atoms were performed using Gaussian 98 program packages. The initial models were constructed by means of breaking bond( s), making bond( s), adding atom( s), deleting atom( s), rotating fragment( s), translating fragment s) and merging fragment( s). The one-fold, two-fold and three-fold modes for modeling were considered, according to the bonding characteristics of the sulfur atom. Finally a total of eleven structures for S-3(+) , S-4(+) and S-5(+) : ten isomers of S-6(+) and S-7(+) ; fifteen isomers of S-8(+) and S-9(+) and thirteen isomers of S-10(+), S-11(+), S-12(+) and S-13(+) are acquired, respectively. A large number of structural possibilities of non-minimum structures were not covered. According to total energies, the most stable S-n(+) ( n = 3 similar to 13) isomers are predicted. The geometry, relative stability and structural rules of these cationic sulfur clusters were described. Some structures of neutral sulfur clusters with true minima transform upon ionization into non-minimum cationic structures and vice versa. The results of a large amount of calculations show that the two-fold coordination is generally favored in sulfur cationic clusters, though some sulfur atoms coordinated with the others in one-fold or three-fold mode 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. In chain structures, the atoms at the two ends adopt the one-fold mode and the others are in two-fold mode. Theoretical studies on sulfur cationic structures with a three-fold atom are rare. It is unlikely to have a sulfur cationic cluster in cage structure, for the bondings of a three-fold atom are not strong enough. The calculation results can serve as guiding factors for future theoretical studies on large sulfur clusters

Structural stabilities of small cationic sulfur clusters

Several isomers of sulfur clusters were acquired by means of geometry optimization and frequency calculations of the B3LYP DFT approach. According to the total energies, the most stable S-n(-) (n = 9similar to13) isomers are of helical configurations. The helical Sn- (n = 14similar to20) structures are also calculated. Most of the anionic clusters are of chain configurations that are completely different from those of the corresponding neutral and cationic clusters in which the ring clusters are in higher total energy