UH和UH2分子的结构与势能函数

用相对论有效原子实势(RECP)和密度泛函(B3LYP/SDD)方法研究了UH,UH₂基态和低激发态的结构和势能函数,导出了分子的光谱数据.结果表明,UH和UH₂的基电子状态分别为X⁴Π和X³A₂,离解能分别为2.886eV和5.249eV,UH₂具有C2v对称性,得到了UH和UH₂的几个不同的低激发态的结构与光谱数据.应用多体项展式理论以及数字拟合方法 关键词： UH 2')" href="#">UH₂ 势能函数 分子结构     

EuC分子的电子态结构和稳定性理论研究

本文分别采用Gaussian98程序的密度泛函B3LYP方法和Gamess程序的CAS-MCSCF方法,研究了EuC分子的结构问题.两种方法均得到了12重态是EuC分子的基态的结论.基于B3LYP方法,得到12∑+态的LUMO和HOMO能量差达到3.689 eV,明显的高于其他多重度的结果.基于MCSCF方法的结果显示,需要进一步的考虑相对论效应修正以及增大活性空间的尺寸将会得到对高自旋电子态更为可靠的结论.     

Pu3体系的结构与势能函数

用相对论有效原子实势(RECP)和密度泛函(B3LYP)方法对Pu_n(n=2,3)体系的结构进行了优化,得到了Pu₂和Pu₃分子的几何构型分别为D_∞h,D_3h,其基态分别为13和19重态.在B3LYP/RECP水平上得到Pu₂分子的光谱常数ω_e=52.3845cm^-1,ω_e　χ_e=0.02 关键词： 2')" href="#">Pu₂ 3')" href="#">Pu₃ 分析势能函数     

The molecular structure and the analytical potential energy function of S2^- and S3^-

In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent （C2v） structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface.     

BeH2(X1Σ+g)与H2S(X1A1)分子的结构与解析势能函数

运用单双取代二次组态相关(QCISD)方法,在6-311++G(3df,3pd)基组水平上,对BeH₂和H₂S分子的结构进行了优化计算,得到基态BeH₂分子的稳定结构为D_∞h构型,电子态为X¹Σ⁺_g,平衡核间距R_BeH=0.13268nm,R_{关键词： 2}')" href="#">BeH₂ 2S')" href="#">H₂S Murrell-Sorbie函数 多体项展式理论 解析势能函数     

Spin polarization effect for Mn2 molecule

The density functional theory method （DFT） （b3p86） of Gaussian 03 has been used to optimize the structure of the Mn2 molecule. The result shows that the ground state of the Mn2 molecule is an 11-multiple state, indicating a spin polarization effect in the Mn2 molecule, a transition metal element molecule. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions of higher-energy states. So the ground state for Mn2 molecule being of an 11-multiple state is the indicative of spin polarization effect of the Mn2 molecule among those in the transition metal elements： that is, there are 10 parallel spin electrons in a Mn2 molecule. The number of non-conjugated electrons is the greatest. These electrons occupy different spacious orbitals so that the energy of the Mn2 molecule is minimized. It can be concluded that the effect of parallel spin in the Mn2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell-Sorbie potential functions with the parameters for the ground state and other states of the Mn2 molecule are derived. The dissociation energy De for the ground state of the Mn2 molecule is 1.4477 eV, equilibrium bond length Re is 0.2506 nm, vibration frequency ωe is 211.51 cm^-1. Its force constants f2, f3, and f4 are 0.7240 aJ·nm-2, -3.35574 aJ·nm^-3, 11.4813 aJ·nm^-4 respectively. The other spectroscopic data for the ground state of the Mn2 molecule ωeχe, Be, αe are 1.5301 cm^-1, 0.0978 cm^-1, 7.7825×10^-4 cm^-1 respectively.     

An ab initio molecular orbital study of the electronically excited and cationic states of the ozone molecule and a comparison with spectral data

A number of valence and Rydberg, singlet and triplet excited states for ozone in the excitation energy range 1–12eV have been calculated by large scale CI methods preceded by MCSCF studies. A comparison of the theoretical intensity envelope with the VUV + EELS spectrum has been made. The present work supports the assignments for the Huggins + Hartley bands as having two electronic origins, 2 ¹A₁ and 1 ¹B₂. The experimental ～ 9.3eV and ～ 10.2eV bands of the VUV spectrum must have adventitious superposition of valence states on Rydberg transitions, because the high oscillator strengths of the valence states cannot be attributed to the 8.8eV broad band. A number of new valence and Rydberg states have been calculated, and these lead to the conclusion that the experimental 9–11 eV VUV spectral range in particular must yield more experimental states than the few so far identified. This suggests a major need for more sophisticated methods of experimental study for the excited state manifolds. The use of various MCSCF/CI studies of the vertical cationic states, supports the IP order as ²A₁ < ²B₂ < ²A₂. A re-analysis of the 12–13.4eV range of the UV-photoelectron band has been performed, with a view to determining the adiabatic IPs more accurately. The present work suggests that the adiabatic IP₂ lies at 12.86eV, slightly lower than has been assumed, with consequential effect on the analysis of the VUV spectrum near 9.4eV.     

AlxOy(x=1—2,y=1—3)分子几何结构与稳定性的DFT研究

用密度泛函理论(DFT)的B31yp方法在6-311++g^水平上对Al_xO_y(x=1—2,y=2—3)分子的几何构型、电子结构、振动频率等性质进行了理论研究. 通过对基态结构的几何参数分析发现，它们的基态结构趋于直线或平面结构. 对基态结构的绝热电离能讨论表明，金属铝原子数一定时，氧原子数从1增加到3，其气态分子越来越稳定，铝原子数少的分子体系更稳定. 系统给出了该系列分子基态的几何参数、电子结构、光谱性质. Al₂O₃的C_2V三重态是该分子的能量最低结构. 关键词： xO_y分子')" href="#">Al_xO_y分子 密度泛函理论 结构与稳定性     

BH2的分子结构和势能函数

采用密度泛函理论(DFT)的B3P86方法和相对论有效原子实势理论模型(RECP)，对BH₂，BH₂⁺和BH₂^-分子进行了优化，得到这些分子基态的电子状态分别是²A′，³A′，³A″. 计算也得到了BH₂的分子结构和势能函数，它的离解能是7.752eV，BH₂分子具有C_{2V关键词： 2}')" href="#">BH₂ 分子结构 势能函数     

SiX2(X=H，F)分子的结构与势能函数

应用QCISD/6-311++G(3df,3pd)和B3P86/6-311++G(3d2f)对SiH₂,SiF₂的结构进行了优化,优化出SiH₂分子的稳定构型为C_2v,电子态为¹A₁,其平衡核间距R_e=0.15149nm、键角∠HSiH=92.5025°、离解能为3.7098eV. SiF _{关键词： 2}')" href="#">SiH₂ 2')" href="#">SiF₂ 多体项展式理论 势能函数     

梯形化合物NaV2O4F电子结构的第一性原理研究

采用基于密度泛函理论(DFT)的第一性原理赝势平面波方法, 通过自旋极化的广义梯度近似(GGA)电子结构计算对梯形化合物NaV₂O₄F进行了研究. 考虑了四种假想的自旋有序态,计算结果表明该化合物的磁基态具有二维反铁磁(AFM)结构, 即沿梯阶和梯腿方向都表现为AFM作用. 能带结构显示NaV₂O₄F为绝缘体材料, 带隙约为1.0eV. 方锥体中的晶体场劈裂使得VO₄F方锥体中的 V^{4+ 关键词： 2O₄F')" href="#">NaV₂O₄F 梯形化合物 第一性原理计算 电子结构}     

自旋-Peierls化合物GeCuO3电子结构的第一性原理研究

采用平面波赝势方法对自旋-Peierls化合物GeCuO₃的电子结构进行了第一性原理研究.计算结果表明：Cu²⁺的3d轨道自由度被冻结,未配对电子填充d_x²-y²轨道.自旋向上和向下的d_x²-y²轨道间的交换劈裂导致了体系的绝缘性.费米能级附近的Cu 3d态与O(2) 2p态存 关键词： 3')" href="#">GeCuO₃ 自旋-Peierls相变 第一性原理计算 共价绝缘体     

BeH,H2和BeH2的分子结构和势能函数

用二次组态相关(QCISD)和密度泛函(B3LYP)方法, 选用6-311++g(d,p), 6-311++g(3df,3pd)和D95(3df,3pd)基组对H₂, BeH和BeH₂分子的结构进行优化. 得到它们的基态电子态分别为H₂(¹Σ_g), BeH(²Σ)和BeH₂(¹Σ_{g 关键词： BeH 2}')" href="#">BeH₂ 2')" href="#">H₂ 二次组态相关(QCISD) 势能函数     

Spin polarization effect of Ni2 molecule

The density functional theory （DFT） method （b3p86） of Gaussian 03 is used to optimize the structure of the Ni2 molecule. The result shows that the ground state for the Ni2 molecule is a 5-multiple state, symbolizing a spin polarization effect existing in the Ni2 molecule, a transition metal molecule, but no spin pollution is found because the wavefunction of the ground state does not mingle with wavefunctions of higher-energy states. So the ground state for Ni2 molecule, which is a 5-multiple state, is indicative of spin polarization effect of the Ni2 molecule, that is, there exist 4 parallel spin electrons in Ni2 molecule. The number of non-conjugated electrons is greatest. These electrons occupy different spatial orbitals so that the energy of the Ni2 molecule is minimized. It can be concluded that the effect of parallel spin in the Ni2 molecule is larger than that of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell-Sorbie potential functions with the parameters of the ground state and other states of the Ni2 molecule are derived. The dissociation energy De for the ground state of the Ni2 molecule is 1.835 eV, equilibrium bond length Re is 0.2243 nm, vibration frequency we is 262.35 cm^-1. Its force constants f2, f3 and f4 are 1.1901 aJ.nm^-2, -5.8723 aJ.nm^-3, and 21.2505 aJ.nm^-4 respectively. The other spectroscopic data for the ground state of the Ni2 molecule ωeχe, Be and αe are 1.6315cm 2, 0.1141 cm^-1, and 8.0145× 10^-4 cm^-1 respectively.     

A multi-reference CI study of the low-lying valence and Rydberg states of CF3 radical

Highly correlated calculations at the multi-reference configuration interaction levels including singles and doubles excitations (MR-CISD) and extensivity corrections (MR-CISD?+?Q) have been performed to study some low-lying valence and Rydberg states of the CF₃ radical. Our highest level results (at the MR-CISD?+?Q level) yield the following energy ordering: 3s (7.90?eV)?2A₂ (8.61?eV)?π (8.72?eV)?z (8.73?eV). MR-CISD results indicate transitions of similar intensities from the ground to the following three final states, in the following order: 3p_π?>?3p_z?>?3s. It has also been found that the aforementioned Rydberg states should be responsible for visible emissions and correspond to transitions between bound states. Therefore, it is suggested that the lack of vibrational structure in the visible band of parent systems (e.g. CF₃Cl) may be due to a transition from a bound to an unbound state of the parent molecule.     

Spin polarization effect for Fe2 molecule

This paper uses the density functional theory （DFT）（B3p86） of Gaussian03 to optimize the structure of Fe2 molecule. The result shows that the ground state for Fe2 molecule is a 9-multiple state, which shows spin polarization effect of Fe2 molecule of transition metal elements for the first time. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions with higher energy states. So, that the ground state for Fe2 molecule is a 9-multiple state is indicative of the spin polarization effect of Fe2 molecule of transition metal elements. That is, there exist 8 parallel spin electrons. The non-conjugated electron is greatest in number. These electrons occupy different spacious tracks, so that the energy of the Fe2 molecule is minimized. It can be concluded that the effect of parallel spin of the Fe2 molecule is laFger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell Sorbie potential functions with the parameters for the ground state and other states of Fe2 molecule are derived. Dissociation energy De for the ground state of Fe2 molecule is 2.8586ev, equilibrium bond length Re is 0.2124nm, vibration frequency we is 336.38 cm^-1. Its force constants f2, f3, and f4 are 1.8615aJ.nm^-2, -8.6704aJ.nm^-3, 29.1676aj.nm^-4 respectively. The other spectroscopic data for the ground state of Fe2 molecule weXe, Be, αe are 1.5461 cm^-1, 0.1339cm^-1, 7.3428× 10^-4 cm^-1 respectively.     

Theoretical study of ground and excited state potential energy surfaces for the Ca+-H2 complex

The potential energy surfaces of the Ca⁺-H₂ complex are calculated using the internally contracted multireference CI method (ICMR CI) and complete active space SCF (CAS SCF) reference wave functions. The calculations involve both the ground and the excited states correlating to (3d)²D and (4p)²P Ca⁺ terms and are carried out for C_∞v and C_2v configurations. Anisotropy of the potential surfaces has also been analysed by computing the interaction energy for some representative points as a function of the angle between the H₂ molecular axis and the Ca⁺—centre of mass of H₂ bond axis. The calculations have revealed the existence of a conical intersection of the lowest excited (3d)²B₂ potential surface with the ground state one. The obtained global energy minimum of the (3d)²B₂ potential surface lying 0.683 eV below the asymptote indicates a possible stabilization of the Ca⁺-H₂ complex towards formation of an exciplex in the (3d)Ca⁺-H₂(v = 0) collision process. The dependence of the vibrational energy levels of H₂ on the distance from Ca⁺ in the C_2v configuration has also been studied.     

BH2和AlH2分子的结构及其解析势能函数

运用二次组态相关(QCISD)方法，分别选用6-311++G(3df,3pd)和D95(3df,3pd)基组，对BH₂和AlH₂分子的结构进行了优化计算，得到BH₂分子的稳态结构为C_2v构型，电子态为²A₁、平衡核间距R_BH=0.1187nm、键角∠HBH=128.791°、离解能D_e=3.65eV、基态振动频率ν₁(a₁)=1020.103cm^-1,ν₂(a₁)=2598.144cm^-1,ν₃(b₂)=2759.304cm^-1.AlH₂分子的稳态结构也为C_2v构型，电子态为²A₁、平衡核间距R_AlH=0.1592nm、键角∠HAlH=118.095°、离解能D_e=2.27eV、基态振动频率ν₁(a₁)=780.81cm^-1,ν₂(a₁)=1880.81cm^-1，ν₃(b₂)=1910.46cm^-1.采用多体项展式理论推导了基态BH₂和AlH₂分子的解析势能函数，其等值势能图准确再现了BH₂和AlH₂分子的结构特征及其势阱深度与位置.分析讨论势能面的静态特征时得到BH+H→BH₂反应中存在鞍点，活化能为150.204kJ/mol；AlH+H→AlH₂反应中也存在鞍点，活化能为54.8064kJ/mol. 关键词： 2')" href="#">BH₂ 2')" href="#">AlH₂ Murrell-Sorbie函数 多体项展式理论 解析势能函数     

MgH分子X2Σ+，A2Π和B2Σ+电子态的势能函数

利用QCISD(T),SAC-CI方法和cc-pVQZ,aug-cc-pVTZ,6-311++G及6-311++G(3df,2pd)基组,对MgH分子的基态X²Σ⁺,第一简并激发态A²Π和第二激发态B²Σ⁺的结构进行优化计算.通过对4个基组计算结果进行比较,得出6-311++G(3df,2pd)基组为最优基组.使用 关键词： 分子结构与势能函数 激发态 Murrell-Sorbie函数 C₆函数')" href="#">Murrell-Sorbie+C₆函数     

SiO2分子的基态(X1A1)结构与分析势能函数

应用群论及原子分子反应静力学方法推导了SiO₂分子的电子态及其离解极限，采用B3P86方法，在6-311G^**水平上,优化出SiO₂基态分子稳定构型为单重态的C_2V构型，其平衡核间距R_e=R_Si—O=0.1587 nm,∠OSiO＝111.2°,能量为-440.4392 a.u..同时计算出基态的简正振动频率:对称伸缩振动频率ν(B₂)=945.4cm^-1，弯曲振动频率ν(A₁)=273.5 cm^-1和反对称伸缩振动频率ν(A₁)=1362.9cm^-1.在此基础上，使用多体项展式理论方法，导出了基态SiO₂分子的全空间解析势能函数，该势能函数准确再现了SiO₂(C_2V)平衡结构.