氨团簇(NH_3)_n(n=2～8)结构的密度泛函理论研究

本文应用密度泛函理论(DFT)的B3LYP方法,在6-31G(d)和6-31 G(d)基组水平上对氨团簇氢键体系进行了研究,计算得到了氨团簇(NH3)n(n=2～8)的各种稳定构型及对应的能量和团簇束缚能.分析发现,在各类尺寸中以单环结构最为稳定,而相同尺寸的异构体之间团簇束缚能越大越稳定.最后利用二阶差分理论讨论了不同尺寸氨团簇中最稳定结构的生长规律,结果表明n=5,7时的结构最为稳定,具有明显的幻数特征,n=6,8时的团簇结构最不稳定,而在n=2～5之间,随着n的增大团簇的稳定性也在逐步增强.     

CuSi6团簇几何结构和性质的密度泛函理论研究

利用密度泛函理论（DFT）的B3LYP方法,采用全电子基组6-311+G（d）研究了CuSi₆团簇的几何构型和电子结构性质,计算表明CuSi₆团簇存在多个能量相近的稳定异构体,且结构中存在多个Cu-Si键,多个低能异构体共存解释了实验中观察到的CuSi₆团簇较强的现象.对于CuSi₆团簇,计算得到的三个最稳定异构体的垂直电离能,电子亲和能和HOMO-LUMO能隙均相对较大,也表明这三个异构体较为稳定.     

CuSi6团簇几何结构和性质的密度泛函理论研究

利用密度泛函理论(DFT)的B3LYP方法,采用全电子基组6-311+G(d)研究了CuSi6团簇的几何构型和电子结构性质,计算表明CuSi6团簇存在多个能量相近的稳定异构体,且结构中存在多个Cu-Si键,多个低能异构体共存解释了实验中观察到的CuSi6团簇较强的现象。对于CuSi6团簇,计算得到的三个最稳定异构体的垂直电离能,电子亲和能和HOMO-LUMO能隙均相对较大,也表明这三个异构体较为稳定。     

苯酚-水团簇C_6H_5OH(H_2O)_n(n=1-6)结构与电子性质的密度泛函理论研究

利用密度泛函理论,在B3LYP/6-31+G(d, p)基组水平上对苯酚-水团簇C_6H_5OH(H_2O)_n(n=1-6)的可能构型进行全优化,得到了团簇的稳定结构;在B3LYP/6-311++G(d, p)基组水平上计算得到了各团簇构型的总能量和结合能,结果显示,在团簇尺寸较小(n≤5)时,团簇C_6H_5OH(H_2O)_n的最稳定结构为平面的环状结构,团簇尺寸较大(n5)时,团簇C_6H_5OH(H_2O)_n的最稳定结构为三维立体结构.通过对团簇结合能的二阶差分、最高占据轨道与最低空轨道之间的能隙、费米能级和电离能的分析发现,团簇C_6H_5OH(H_2O)_2的最低能量结构具有较高的稳定性,可能具有幻数结构.     

关于Al_nC和Al_nC~+(n=1—8)团簇结构和稳定性的研究

通过采用7种密度泛函理论DFT方法对AlnC进行计算,所得结果与实验数据比较,选择了B3lyp方法和6-311G(d)基组对AlnC及AlnC+(n=1—8)团簇进行结构优化和频率分析,得到了AlnC及AlnC+基态以及亚稳态结构.当n从小到大变化时,这些团簇的结构从平面向立体过渡,平面构型以三角形为主,立体构型主要是三棱柱笼状结构;在这些团簇中的高对称性结构中,中性团簇和阳离子只能有其一是稳定构型;在所研究的团簇中,Al2C和Al5C团簇较为稳定.     

NH3(H2O)4稳定结构的理论研究

先构建氨水团簇的模型势,并计算得到NH3(H2O)4的模型势异构体,从中选取稳定性较好的异构体作为初始结构,分别利用密度泛函方法和二级微扰理论在6-31G(d)和6-311++G(d,p)基组水平上逐级进行结构优化、频率和单点能计算.发现包括第2和第3稳定结构等12种新异构体;NH3(H2O)4的五边形环状结构的稳定性最好;这种极性混合分子簇的偶极矩大小和包含的氢键数都与结构的稳定性无必然联系.     

一种新的C32异构体

我们构造出一种新的类笼形C32异构体, 不包含五边形和六边形结构,具有D2h对称性.采用密度泛函理论DFT的rb3lyp方法在6-31G(d)基组水平上进行了相关计算 .计算结果表明它是一种稳定的构型.     

苯系物Cu_3金属配合物的结构与性质的理论研究

采用密度泛函理论的B3LYP方法,在6-311+G(d,p)基组水平上计算研究了Cu_3团簇与甲苯、二甲苯、三甲苯分子作用的各种异构体结构和频率,比较各异构体间的能量关系,得到最稳定的几何构型.通过分析Cu_3和苯系列化合物作用的结合能和前线轨道等性质,从而了解该类配合物的作用机理.     

吡啶-水团簇(C_5H_5N)_n(H_2O)_m(n=1～2,m=1～4)结构和红外光谱的理论研究

利用密度泛函理论,在B3LYP/6-311++G(d,p)基组水平上对吡啶-水团簇(C5H5N)n(H2O)m(n=1~2,m=1~4)的可能构型进行全优化,得到了团簇的稳定结构;计算结果显示,在吡啶和水的二聚体中,稳定构型只有一种,没有发现通过π氢键(O—H…π)作用形成的团簇结构。为了研究各团簇结构的稳定性,在相同的基组水平上计算得到了各团簇构型的总能量和结合能,结果显示,对于团簇(C5H5N)n(H2O)4(n=1~2),团簇中的水分子形成四元环的结构要比形成三元环的结构稳定。对团簇的最高占据轨道与最低空轨道之间的能隙分析发现,团簇C5H5N(H2O)4的最低能量结构具有较高的稳定性,可能具有幻数结构;最后,分析讨论了吡啶-水团簇的红外振动光谱,对较强的谱峰进行了指认。     

(Ca3N2)n(n=1-4)团簇结构与性质的密度泛函理论研究

用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对(Ca3N2)n(n=1-4)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的振动特性、成键特性、电荷特性和稳定性等进行了理论分析.结果表明,(Ca3N2)n(n=1-4)团簇最稳定构型中N原子为3-5配位,Ca-N键长为0.231-0.251 mm,Ca-Ca键长为0.295-0.358 nm;N原子的自然电荷在-1.553 e--2.241 e之间,Ca原子的自然电荷在1.035e-1.445e之间,Ca和N原子间相互作用呈现较强的离子性,Ca3N2和(Ca3N2)3团簇有相对较高的动力学稳定性.     

Theoretical investigation on structures,stability and properties of [P,X, Y] (X=C,Si; Y = O,S) isomers

The structures, energetics and stability of the [P, X, Y] (X?=?C, Si; Y?=?O, S) radicals are explored by means of the density functional theory and ab initio levels. Seventeen [P, X, Y] isomers and 14 interconversion transition states are obtained at the B3LYP/6-311G(d) level. At the CCSD(T)/6-311?+?G(2df)//QCISD/6-311G(d)?+?ZPVE level, the lowest-lying isomers are the linear PCO 1a (0.0?kcal/mol), PCS 1b (0.0) and the three-membered ring cPSiO 1c (0.0), cPSiS 1d (0.0) on their respective potential energy surfaces. These four isomers exhibit considerably not only thermodynamic but also kinetic stabilities. Additionally, the cyclic cPCS 2b (32.8) and linear PSiS 2d (18.6) possess also high kinetic stability. All of six isomers 1a, 1b, 2b, 1c, 1d and 2d are considerably stabilized by a barrier of at least 20?kcal/mol, and may be detected in the laboratory or interstellar space. Their valence bond structures and possible formation strategies in the laboratory and space are discussed in detail. Finally, the similarities and discrepancies on structures and stabilities between [P, X, Y] (X?=?C, Si; Y?=?O, S) isomers are compared. These predicted results are highly expected to be informative for the future identification of [P, X, Y] (X?=?C, Si; Y?=?O, S) in the laboratory and space.     

Co@Aun(n=1-8)团簇的几何结构和电子性质的理论研究

本文利用密度泛函PW91方法研究了Co@Aun(n=1-8)团簇的平衡结构、稳定性和磁矩。结构优化显示Co原子在低能异构体中趋于占据最高配位位置,基态Co@Aun(n=2-6)团簇为二维结构,Co@Au7和Co@Au8转变为三维结构。原子平均结合能、二阶能量差分及HOMO-LUMO能级间隙分析表明掺杂Co原子提高了金团簇的稳定性,改变了金团簇能级间隙的奇偶振荡性,n=5为掺杂团簇的幻数。磁矩的计算揭示Co@Aun团簇的磁性主要源于Co原子的3d轨道。     

Co@Au_n(n=1～8)团簇的几何结构和电子性质的理论研究

本文利用密度泛函PW91方法研究了Co@Au_n（n=1～8）团簇的平衡结构、稳定性和磁矩.结构优化显示Co原子在低能异构体中趋于占据最高配位位置,基态Co@Au_n（n=2～6）团簇为二维结构,Co@Au₇和Co@Au8转变为三维结构.原子平均结合能、二阶能量差分及HOMO-LUMO能级间隙分析表明掺杂Co原子提高了金团簇的稳定性,改变了金团簇能级间隙的奇偶振荡性,n=5为掺杂团簇的幻数.磁矩的计算揭示Co@Au_n团簇的磁性主要源于Co原子的3d轨道.     

Structures and stability of N13 cluster

Quantum chemical studies for the nine N₁₃ isomers with low spin were carried out at the UHF/6-31G*, UB3LYP/6-31G* and UMP2/6-311G* levels of theory. The most stable N₁₃ isomer is structure 1 with C_2v symmetry, which contains two separated pentazole rings connected by three nitrogen atoms. The results show that structures 1, 2, 3, 4 and 5 which are composed of the pentazole ring are more stable than the open chain structure 6 and structures 8 and 9 which contain the four- and six-membered rings. This suggests that the pentazole ring is a fundamental stable structural unit, which is applicable not only for the even-numbered nitrogen clusters, but also for the large odd-numbered clusters.     

Density functional theory study on the structure and properties of Si3N4clusters

The hybrid density functional theory B3LYP with basis sets 6-31G· has been used to study on the equilibrium geometries and electronic structures of possible isomers of Si3N4 clusters. 24 possible isomers are obtained. The most stable isomer of Si3N4 is a 3D structure with 7 Si-N bonds and 2 N-N bonds that could be formed by 3 quadrangles. The bond properties of the most stable isomer was analyzed by using natural bond orbital method (NBO), the results suggest that the charges on Si and N atoms in Si-N bonds are quite large, so the interaction of N-Si atoms in Si3N4 cluster is of strongly electric interaction. The primary IR and Raman vibrational frequency located at 1033.40 cm-1, 473.63 cm-1 respectively. The polarizabilities and hyperpolarizabilities of the most stable isomer are also analyzed.     

Structure and stability of neutral and cationic AlnO clusters

In this paper various structural possibilities for AlnO neutral and cationic isomers were investigated by using the B3LYP/6-311G（3df） method. Calculations of this paper predicted the existence of a number of previously unknown isomers. The stabilities of the AlnO （n = 2 - 7） clusters with even n are greater than those with odd n, however the stabilities Of cationic ions have the opposite odd-even alternation. The mass spectra observations of Al17O^＋ and Al19O^＋ ions support our theoretical predictions on their stabilities.     

多硝基六氮杂金刚烷结构和相对稳定性的理论研究

基于密度泛函理论,在B3LYP/6-31G*水平下分别计算了潜在高能量密度化合物(HEDC)多硝基六氮杂金刚烷(PNHAAs)的结构,包括总能量、几何结构、氧平衡、偶极矩等．通过研究PNHAAs的结构参数,如N-NO2最大键长、N-NO2键的最小Mulliken集居数、-NO2所带最小负电荷、氧平衡,预测了10个标题物的相对稳定性或感度(起爆的难易程度．感度越高,化合物的稳定性越低)．结果发现,这四个参数基本上能得到一致的结论:随着硝基数目的增加,标题物的稳定性降低．氧平衡不能判别同分异构体的相对稳定性,但总能量和偶极矩可较好地判别同分异构体的相对稳定性．     

First-Principles Study of Geometries,Stabilities and Electronic Properties of Ca2Sin （n=1-11） Clusters

The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin （n = 1-11） dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed.     

(AgBr)6结构计算及对计算方法的依赖

利用HF、B3LYP方法分别结合LANL2DZ,CEP-121G赝势基组及3-21G*全电子基组对(AgBr)6的可能异构体进行结构优化。结果显示,HF、B3LYP方法在各基组水平上优化的(AgBr)6基态结构并不完全一致,表明(AgBr)6结构计算对计算方法具依赖性。对优化后能量始终较低的5个结构,进一步采用MP2方法结合上述基组进行高精度的结构优化。确定(AgBr)6基态结构为双三角形环重叠结构,并计算了该结构的红外光谱。     

(AgBr)6结构计算及对计算方法的依赖

利用HF、B3LYP方法分别结合LANL2DZ,CEP-121G赝势基组及3-21G*全电子基组对(AgBr)6的可能异构体进行结构优化。结果显示,HF、B3LYP方法在各基组水平上优化的(AgBr)6基态结构并不完全一致,表明(AgBr)6结构计算对计算方法具依赖性。对优化后能量始终较低的5个结构,进一步采用MP2方法结合上述基组进行高精度的结构优化。确定(AgBr)6基态结构为双三角形环重叠结构,并计算了该结构的红外光谱。