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1.
Some low‐lying states of HAlO+ and HOAl+ cations have been studied using the complete‐active‐space self‐consistent field (CASSCF) and multiconfiguration second‐order perturbation theory (CASPT2) methods with the contracted atomic natural orbital (ANO) basis sets. The geometries of all stationary points along the potential energy surfaces were optimized at the CASSCF/ANO and CASPT2/ANO levels. The ground and the first excited states of HAlO+ are predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HOAl+ is X2Σ+ state. The A2Π state of HOAl+ has unique imaginary frequency. A bent local minimum M1 was found along the 12A″ potential energy surface, and the A2Π state of HOAl+ should be the transition state of the isomerization reactions for M1 ? M1. The CASPT2/ANO potential energy curves of isomerization reactions were calculated as a function of HAlO bond angle. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

2.
The HBO+ and HOB+ cations have been reinvestigated using the CASSCF and CASPT2 methods in conjunction with the contracted atomic natural orbital (ANO) basis sets. The geometries of all stationary points in the potential energy surfaces were optimized at the CASSCF/ANO and CASPT2/ANO levels. The ground and the first excited states of HBO+ are predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HOB+ is X2Σ+ state. The A2Π state of HOB+ has unique imaginary frequency. A bending local minimum M1 was found for the first time along the 12A′′ potential energy surface and the A2Π state of HOB+ should be the transition state of the isomerization reactions for M1? M1. The CASPT2/ANO potential energy curves (PECs) of isomerization reactions were calculated as functions of the HBO bond angle. Many of the CASSCF and CASPT2 calculated results were different from the previously published QCISD(T) results. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   

3.
In this study, some low‐lying states of the HBN and HNB radicals have been studied using multiconfiguration second‐order perturbation theory. The geometries of all stationary points along the potential energy surfaces (PESs) were optimized at the CASPT2/cc‐pVQZ level. The ground and the first excited states of HBN were predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HNB is X2Σ+ state. The A2Π state of HNB has unique imaginary frequency, which was different from the previously published results. A bending local minimum M1 was found for the first time along the 12A″ PES, and the A2Π state of HNB should be the transition state of the isomerization reactions for M1 ? M1. The CASPT2/ANO potential energy curves (PECs) of isomerization reactions for HBN ? HNB were calculated as a function of HBN bond angle. By comparing the CASPT2 and CASSCF calculated results, we concluded that the influence of the dynamic electron correlation on HBN ? HNB system is not large. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

4.
The HBeN? and HNBe? anions have been investigated for the first time using the CASSCF, CASPT2, and DFT/B3LYP methods with the contracted atomic natural orbital (ANO) and cc‐pVTZ basis sets. The geometries of all stationary points along the potential energy surfaces were optimized at the CASSCF/ANO and B3LYP/cc‐pVTZ levels. The ground and the first excited states of HBeN? are predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HNBe? is X2Σ+ state. The A2Π state of HNBe? has unique imaginary frequency. A bend local minimum M1 was found along the 12A″ potential energy surface and the A2Π state of HNBe? should be the transition state of the isomerization reactions for M1 ? M1. The CASPT2/ANO potential energy curves of isomerization reactions were calculated as a function of HBeN bond angle. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010  相似文献   

5.
Some low‐lying states of the HAlS+ and HSAl+ cations have been studied for the first time by large‐scale theoretical calculations using three methods: complete active space self‐consistent field (CASSCF), complete active second‐order perturbation theory (CASPT2), and density functional theory Becke's three‐parameter hybrid function with the nonlocal correlation of Lee–Yang–Parr (B3LYP) with the contracted atomic natural orbital (ANO‐L) and cc‐pVTZ basis sets. The geometries of all stationary points along the potential energy surfaces (PESs) were optimized at the CASSCF/ANO‐L and B3LYP/cc‐pVTZ levels. The ground and the first excited states of linear HAlS+ are predicted to be X2Π and A2Σ+ states, respectively. For the linear HSAl+ structure, the first excited state is A2Σ+. The X2Π state of linear HSAl+ is a second‐order saddle point, because it has two imaginary frequencies. Two bent global minima M1 and M2 were found along the 12A′ and 12A″ PESs, respectively. The CASPT2/ANO‐L potential energy curves of isomerization reactions were calculated as a function of HAlS bond angle. According to our calculations, the ground‐state HAlS+ is linear, whereas the ground‐state HSAl+ is bent. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

6.
The HBC? and HCB? anions have been studied using the complete active space self‐consistent field, CASPT2, and DFT/B3LYP methods with the contracted atomic natural orbital (ANO) and cc‐pVTZ basis sets. The geometries of all stationary points along the potential energy surfaces were optimized at the CASSCF/ANO and B3LYP/cc‐pVTZ levels. The ground state of HBC? is predicted to be X2? state, which is different from the previously published results. The CASPT2/ANO potential energy curves (PECs) of isomerization reactions were calculated as a function of HBC bond angle and the PECs also show the 2? state is the ground state of HBC? anion. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009  相似文献   

7.
The CASPT2 potential energy curves (PECs) for O‐loss dissociation from the X2Π, A2Π, B2Σ+, C2Σ+, 14Σ?, 12Σ?, and 14Π states of the OCS+ ion were calculated. The PEC calculations indicate that X2Π, 14Σ?, 12Σ?, and 14Π correlate with CS+(X2Σ+) + O(3Pg); A2Π and B2Σ+ correlate with CS+(A2Π) + O(3Pg); and C2Σ+ probably correlates with CS+(X2Σ+) + O(1Dg). The CASSCF minimum energy crossing point (MECP) calculations were performed for the C2Σ+/14Σ?, C2Σ+/14Π, A2Π/14Σ?, A2Π/12Σ?, A2Π/14Π, and B2Σ+/12Σ? state pairs and the spin‐obit couplings were calculated at the located MECPs. A conical intersection point between the B2Σ+ and C2Σ+ potential energy surfaces was found at the CASSCF level. Based on our calculations, seven O‐loss predissociation processes of the C2Σ+ state are suggested and an appearance potential value of 7.13 eV for the CS+ + O product group is predicted. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

8.
The density functional theory (DFT) and the complete active space self‐consistent‐field (CASSCF) method have been used for full geometry optimization of carbon chains C2nH+ (n = 1–5) in their ground states and selected excited states, respectively. Calculations show that C2nH+ (n = 1–5) have stable linear structures with the ground state of X3Π for C2H+ or X3Σ? for other species. The excited‐state properties of C2nH+ have been investigated by the multiconfigurational second‐order perturbation theory (CASPT2), and predicted vertical excitation energies show good agreement with the available experimental values. On the basis of our calculations, the unsolved observed bands in previous experiments have been interpreted. CASSCF/CASPT2 calculations also have been used to explore the vertical emission energy of selected low‐lying states in C2nH+ (n = 1–5). Present results indicate that the predicted vertical excitation and emission energies of C2nH+ have similar size dependences, and they gradually decrease as the chain size increases. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009  相似文献   

9.
Geometries, frequencies, and energies of the 12B1, 12A2, 12B2, 22B1, 22B2, and 12A1, of the C6H5Br+ ion were calculated by using CASSCF and CASPT2 methods in conjunction with an ANO‐RCC basis. The CASPT2//CASSCF adiabatic excitation energies and CASPT2 relative energies for the six states are in good agreement with experiment. The X, A, B, C, and D electronic states of the C6H5Br+ ion were assigned to be X2B1, A2A2, B2B2, C2B1, and D2B2 based on the CASSCF and CASPT2 calculations. The assignment on the D state of the C6H5Br+ ion is different from the previously published works. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010  相似文献   

10.
Theoretical potential energy curves are computed for the X 2Σ+ and A 2Π states of CsO using a relativistic effective core potential and a large valence Gaussian basis set. Seventeen electrons are correlated by a CI (SD ) calculation from each HF reference. We find the X 2Σ+ state lower by 497 and 726 cm?1 at the HF and CI(SD) levels. Our calculated ωe of 312 cm?1 for the X 2Σ+ state agrees well with experimental values deduced from studies in matrices.  相似文献   

11.
Silicon atoms react under single collision conditions with N2O to yield chemiluminescent emission corresponding to the SiO a3Σ+?X1Σ+ and b3Π?X1Σ+ intercombination systems and the A1Π?X1Σ+ band system. A most striking feature of the SiN2O reaction is the energy balance associated with the formation of SiO product molecules in the A1Π and b3Π states. A significant energy discrepancy ( = 10000 cm? = 1.24 eV) is found between the available energy to populate the highest energetically accessible excited-state quantum levels and the highest quantum level from which emission is observed. It is suggested that this discrepancy may result from the formation of vibrationally excited N2 in a concerted fast SiN2O reactive encounter. Emission from the SiO a3Σ+ (A1Π) and b3Π(A1Π, E1Σ0+) triplet-state manifold results primarily from intensity borrowing involving the indicated singlet states. Perturbation calculations indicate the magnitude of the mixing between the b3Π, A1Π and E1Σ0+ states ranges between 0.5 and 2%. On the basis of these calculations, the branching ratio (excited triplet)/(excited singlet) is found to be well in excess of 500. An approximate vibrational population distribution is deduced for those molecules formed in the b3Π state. The present studies are correlated with those of previous workers in order to provide an explanation for diverse relaxation effects as well as observed changes in the ratio of a3Σ+ to b3Π emission as a function of pressure and experimental environment. Some of these effects are attributable to a strong coupling between the a3Σ+ and b3Π state. Based on the current results, there appears to be little correlation between either (1) the branching ratio for excited state formation or (2) the total absolute cross section for excited-state formation and (3) the measured quantum yield for the SiN2O reaction. Implications for chemical laser development are considered.  相似文献   

12.
Potential energy curves for low-lying states of BH+ dissociating to B+(1S) + H, B+(3P) + H and B(2P) + H+ have been determined by ab initio calculations. Agreement between experimental and calculated values of the spectroscopic constants for the X2Σ+and A2Π states supports the theoretical predictions concerning the bound B' 2Σ+ state. The 32+ and 22Π states are predicted to be repulsive.  相似文献   

13.
OH自由基的高精度量子化学研究   总被引:6,自引:0,他引:6  
采用内收缩MRCI方法(Internally Contracted Multiconfiguration-Reference Configuration Interaction)研究了OH自由基, 计算得到其基态稳定构型的键长是0.09708 nm, 对应的实验值是0.096966 nm, 第一激发态的键长是0.10137 nm,实验值是0.10121 nm. 同时得到势能曲线PECs (Potential Energy Curve), 再分别由Murrell-Sorbie势能函数拟合计算和POLFIT程序计算得到OH自由基在基态X2Π和第一激发态A2Σ+时的光谱数据:平衡振动频率ωe, 非谐性常数ωeχe以及高阶修正ωeYe, 平衡转动常数Be, 振转耦合系数αe, 解离能D0和垂直跃迁能量ν00. 这些理论计算结果与最新的实验值非常吻合, 精确度比前人也有很大提高. 其中我们计算得到基态OH(X2Π)的解离能D0=35568.86 cm-1, 第一激发态OH (A2Σ+)的解离能D0=18953.93 cm-1, 从第一激发态A2Σ+ (ν=0)到基态X2Π (v=0)的垂直跃迁能ν00=32496.42 cm-1.  相似文献   

14.
Relativistic configuration interaction calculations are carried out to study the electronic structure and spectroscopic properties of InI and InI+. Potential energy curves of the ground and a number of low‐lying states are constructed. Spectroscopic parameters of the bound states of both species are computed and compared with the experimental and other theoretical data. Effects of spin‐orbit coupling on the spectroscopic properties are studied. Because of the presence of the heavy atoms the effect is large. The spin‐orbit splitting of the ground state (X2Π) of InI+ is more than 8350 cm?1. As a result of the strong spin‐orbit interaction between X2Π and A2Σ+ of InI+, the potential energy curve of A2Σ becomes repulsive. Radiative lifetimes for the spin‐forbidden transitions such as A3Π?X1Σ and B3Π1 ?X1Σ of InI and spin‐allowed transitions such as B2Σ+?A2Σ+, C2Π?A2Σ+, and B2Σ+?X2Π are calculated. Vertical and adiabatic ionization energies of InI and the electric dipole moments of both the neutral and ionic species are estimated. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010  相似文献   

15.
Magnesium monofluoride (MgF) is proposed as an ideal candidate radical for direct laser cooling. Here, the rotationally resolved laser spectra of MgF for the A2Π-X2Σ+ electronic transition system were recorded by using laser induced fluorescence technique. The MgF radicals were produced by discharging SF6/Ar gas mixtures between the tips of two magnesium needles in a supersonic jet expansion. We recorded a total of 19 vibrational bands belonging to three sequences of Δv=0, ±1 in the region of 348-370 nm. Accurate spectroscopic constants for both X2Σ+ and A2Π states are determined from rotational analysis of the experimental spectra. Spectroscopic parameters, including the Franck-Condon factors (FCFs), are determined from the experimental results and the Rydberg-Klein-Rees (RKR) calculations. Significant discrepancies between the experimentally measured and RKR-calculated FCFs are found, indicating that the FCFs are nearly independent of the spin-orbit coupling in the A2Π state. Potential energy curves (PECs) and FCFs determined here provide necessary data for the theoretical simulation of the laser-cooling scheme of MgF.  相似文献   

16.
Results of CASSCF state-averaged calculations on the lowest electronic states of LaO and LaO+ are reported in this work. For comparison, some low-lying electronic states of AlO and AlO+ are also reported. The ground state of LaO was found to be the X2Σ+ (Re = 1.987 Å, ωe = 794 cm?1) with a low-lying A2Δ excited state. Five more excited states below 26000 cm?1 were found. The first ionization potential (IP ) is found at 5.16 eV, resulting in an X1Σ+ ground state for the LaO+ diatom, in opposition to AlO+ for which an X3 Π ground state has been found. Analysis of the wave functions, dipole moments, and Mulliken populations reveal that the bonding is quite ionic in both systems. © 1994 John Wiley & Sons, Inc.  相似文献   

17.
Complete active space self‐consistent field (CASSCF) and multiconfiguration second‐order perturbation theory (CASPT2) calculations with contracted ANO‐RCC basis set were performed for low‐lying electronic states of CH3SS and its cation in Cs symmetry. For the ground state X2A″ of CH3SS, the calculated S‐S stretching mode is in good agreement with experimental reports. The electron transitions of CH3SS+, X1A′ → 11A″, X1A′ → 21A′, and X1A′ → 21A″, are predicted at 1.055, 3.247, and 3.841 eV. Moreover, the calculated adiabatic and vertical ionization potential and adiabatic affinity are in reasonable agreement with the experimental data. The CASSCF/CASPT2 potential energy curves (PECs) were calculated for S2‐loss dissociation from the X2A″, 12A′, and 22A″ states. The electronic states of the CH3 radical and S2 molecule as the dissociation products were carefully determined by checking energies and geometries of the asymptote products. The S2‐loss PEC for CH3SS indicate that S2‐loss dissociation occurs from the X2A″ state leading to CH3 (12A″) + S2 (X3Σ), the 12A′ and 22A″ leading to CH3 (12A″) + S2 (1Δg). © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012.  相似文献   

18.
Summary The dipole moments and dipole polarizabilities of the 1A1, 1B1, and 3B1 electronic states of the water molecule have been calculated by using the CASSCF approach followed by the evaluation of the dynamic electron correlation contribution by the second-order perturbation scheme CASPT2. All calculations have been carried out in a specifically extended ANO basis set which accounts for the Rydberg character of the two excited states. In order to estimate the correctness and accuracy of the present data a scan over a variety of different active spaces for the CASSCF wave function has been made. The present results are superior to earlier CASSCF calculations, although their qualitative features remain essentially the same. The dipole moments in 1B1 and 3B1 states are predicted to be about 0.49 a.u. and 0.33 a.u., respectively, and have the opposite orientation with respect to the ground state dipole moment. The dipole polarizability tensors of the excited states are characterized by high anisotropy and are dominated by the in-plane component perpendicular to the symmetry axis. All their components are found to be about an order of magnitude larger than those of the ground state polarizability tensor. The excitation energy dependence on the choice of the active orbital space in the CASSCF reference function is also considered and the analysis of the present data concludes in the concept of what is called the mutually compatible active spaces for the two states involved in excitation. All CASPT2 results are in good agreement with the results of recent calculations carried out in the framework of the open-shell coupled cluster formalism. This agreement confirms the high efficiency of the CASSCF/CASPT2 approach to the treatment of the electron correlation effects.  相似文献   

19.
Complete active space self‐consistent field (CASSCF) and complete active space second‐order perturbation theory (CASPT2) calculations in conjunction with the aug‐cc‐pVTZ basis set have been used to investigate the low‐lying electronic states of thiofulminic acid (HCNS), HCNS+, and HCNS?. The result of geometry optimization using CASPT2/aug‐cc‐pVTZ shows that theoretically determined geometric parameters and harmonic vibrational frequencies for the HCNS ground state X1Σ+(X1A′) are in agreement with previous studies. The ionization energies, the electron affinity energies, the adiabatic excitation energies, and vertical excitation energies have been calculated and the corresponding cation and anion states are identified. By calculating adiabatic electron affinity, the states of HCNS? have been identified to contain both π orbital states (X2A′ and 12A″) and dipole‐bond states (14A′ and 14A″). © 2012 Wiley Periodicals, Inc.  相似文献   

20.
In the present work, we mainly study dissociation of the C 2B1, D2A1, and E2B2 states of the SO2+ ion using the complete active‐space self‐consistent field (CASSCF) and multiconfiguration second‐order perturbation theory (CASPT2) methods. We first performed CASPT2 potential energy curve (PEC) calculations for S‐ and O‐loss dissociation from the X, A, B, C, D, and E primarily ionization states and many quartet states. For studying S‐loss predissociation of the C, D, and E states by the quartet states to the first, second, and third S‐loss dissociation limits, the CASSCF minimum energy crossing point (MECP) calculations for the doublet/quartet state pairs were performed, and then the CASPT2 energies and CASSCF spin‐orbit couplings were calculated at the MECPs. Our calculations predict eight S‐loss predissociation processes (via MECPs and transition states) for the C, D, and E states and the energetics for these processes are reported. This study indicates that the C and D states can adiabatically dissociate to the first O‐loss dissociation limit. Our calculations (PEC and MECP) predict a predissociation process for the E state to the first O‐loss limit. Our calculations also predict that the E2B2 state could dissociate to the first S‐ and O‐loss limits via the A2B2E2B2 transition. On the basis of the 13 predicted processes, we discussed the S‐ and O‐loss dissociation mechanisms of the C, D, and E states proposed in the previous experimental studies. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   

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