共查询到20条相似文献,搜索用时 31 毫秒
1.
采用二阶微扰理论MP2、密度泛函B3LYP方法和含时密度泛函TD-B3LYP方法分别优化了TiO2分子的基态1A1和六个激发态1B2、3B2、1B1、3B1、1A2和3A2的几何结构. 1A1、1B2、3B2、1B1和3B1具有弯曲几何结构, 1A2和3A2具有线性对称结构. 我们发现激发态1B2、3B2、1B1和3B1键偶极矩的数值大小顺序和相应的键角大小顺序完全一致. 另外, 采用完全活化空间自洽场(CASSCF)CASSCF(6,6)、CASSCF(8,8)、多参考组态相互作用(MRCI)和含时密度泛函TD-B3LYP 计算了TiO2 分子各激发态的垂直激发能和绝热激发能. 对1B2、3B2和1B1三个态, MRCI/CASSCF(6,6) 计算的垂直激发能和绝热激发能与已有的实验值最接近. 对其他三个激发态3B1、1A2和3A2, 计算的激发能和文献报道的激发能计算值基本一致. 最后, 还计算了TiO2分子的基态和激发态的偶极矩. 对1A1和1B2态, 偶极矩的计算值与已有的实验值相吻合. 采用原子偶极矩校正的Hirshfeld 布居方法计算了TiO2分子在1A1、1B2、3B2、1B1和3B1态时各原子的电荷, 发现从基态到激发态偶极矩的变化与电荷从氧原子向钛原子的转移有关. 整个计算中还考察了基函数cc-pVDZ、cc-pVTZ和cc-pVQZ对计算结果的影响. 相似文献
2.
Summary The dipole and quadrupole moments and the dipole polarizability tensor components are calculated for the1
B
1 and3
B
1 excited states of the water molecule by using the complete active space (CAS) SCF method and an extended basis set of atomic natural orbitals. The dipole moment in the lowest1
B
1 (0.640 a.u.) and3
B
1 (0.416 a.u.) states is found to be antiparallel to that in the ground electronic state of H2O. The shape of the quadrupole moment ellipsoid is significantly modified by the electronic excitation to both states investigated in this paper. All components of the excited state dipole polarizability tensor increase by about an order of magnitude compared to their values in the ground electronic state. The present results are used to discuss some aspects of intermolecular interactions involving molecules in their excited electronic states. 相似文献
3.
Wen‐Zuo Li Jian‐Bo Cheng Qing‐Zhong Li Bao‐An Gong Jia‐Zhong Sun 《International journal of quantum chemistry》2010,110(14):2683-2688
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
4.
The electronic structure of azulene molecule has been studied. We have obtained the optimized structures of ground and singlet excited states by using the complete active space self-consistent-field (CASSCF) method, and calculated vertical and 0-0 transition energies between the ground and excited states with second-order M?ller-Plesset perturbation theory (CASPT2). The CASPT2 calculations indicate that the bond-equalized C(2v) structure is more stable than the bond-alternating C(s) structure in the ground state. For a physical understanding of electronic structure change from C(2v) to C(s), we have performed the CASSCF calculations of Duschinsky matrix describing mixing of the b(2) vibrational mode between the ground (1A(1)) and the first excited (1B(2)) states based on the Kekule-crossing model. The CASPT2 0-0 transition energies are in fairly good agreement with experimental results within 0.1-0.3 eV. The CASSCF oscillator strengths between the ground and excited states are calculated and compared with experimental data. Furthermore, we have calculated the CASPT2 dipole moments of ground and excited states, which show good agreement with experimental values. 相似文献
5.
Dr. Chih‐Kai Lin Dr. Yingli Niu Prof. Chaoyuan Zhu Prof. Zhigang Shuai Prof. Sheng Hsien Lin 《化学:亚洲杂志》2011,6(11):2977-2985
The geometric, energetic, and spectroscopic properties of the ground state and the lowest four singlet excited states of pyrazine have been studied by using DFT/TD‐DFT, CASSCF, CASPT2, and related quantum chemical calculations. The second singlet nπ* state, 1Au, which is conventionally regarded dark due to the dipole‐forbidden 1Au←1Ag transition, has been investigated in detail. Our new simulation has shown that the state could be visible in the absorption spectrum by intensity borrowing from neighboring nπ* 1B3u and ππ* 1B2u states through vibronic coupling. The scans on potential‐energy surfaces further indicated that the 1Au state intersects with the 1B2u states near the equilibrium of the latter, thus implying its participation in the ultrafast relaxation process. 相似文献
6.
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 A2B2 ← E2B2 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
7.
Jinglai Zhang Yonghong Li Junfeng Li Xing Chen Zexing Cao 《International journal of quantum chemistry》2009,109(5):1116-1126
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
8.
In this work we analyze how the choice of the active space in the CASSCF (the complete-active-space multiconfiguration self-consistent-field method) and CASPT2 (the second-order perturbation theory based on the CASSCF reference wave function) calculations affects the computed potential energy curves (PECs) for the intramolecular proton transfer reaction in the ground state and the two lowest lying singlet excited states of 1-amino-3-propenal. As anticipated, the results revealed that, qualitatively, the proton transfer in the different states can be correctly described even by minimal active spaces, which include the orbitals involved in the electronic excitation of the considered state and the antibonding sigma orbital corresponding to the bond formed by the molecule with the migrating hydrogen atom. However, quantitatively, the relative energies of the two tautomers and the energy barriers computed at the CASSCF level change when the active space is increased, indicating importance of the dynamic electron correlation. Introducing the dynamic correlation effects via CASPT2 makes the calculated energy parameters more uniform among the different active spaces. The analysis suggested certain optimal active spaces for studying proton transfer reactions in systems similar to 1-amino-3-propenal. The PEC calculations for excited states showed that the results are sensitive to the molecular geometries used in the calculations, particularly near the transition point. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1422–1431 (1999) 相似文献
9.
Chui‐Peng Kong Zeng‐Xia Zhao Hong‐Xing Zhang 《International journal of quantum chemistry》2013,113(9):1416-1421
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
10.
采用CASSCF方法和6-311++(3df, 3pd)基组以及Cs对称性优化了乙基硫自由基和阳、阴离子3种分子的12个电子态的几何构型. 利用二级微扰方法(CASPT2)对这12个电子态做了单点能校正. 通过比较自由基与阴阳离子的能量, 得出了绝热电子亲和势和绝热电子电离能, 与实验结果在允许误差范围内基本一致. 相似文献
11.
Summary The electronic spectra forcis-1,3-butadiene andcis-1,3,5-hexatriene have been studied using multiconfiguration second-order perturbation theory (CASPT2) and extended ANO basis sets. The calculations comprise all singlet valence excited states below 8.0 eV, the first 3s, 3p, 3d Rydberg states, and the second 3s state. The four lowest triplet states were also studied. The resulting excitation energies forcis-hexatriene have been used in an assignment of the experimental spectrum, leading to a maximum deviation of 0.13 eV for the vertical transition energies. The calculations place the 11
B
2 state 0.04 eV below the 21
A
1 state. 16 excited states were studied incis-butadiene, using a CASPT2 optimized ground state geometry. The 11
B
2 state was located at 5.58 eV, 0.46 eV below the 21
A
1 state and 0.09 eV above the experimental value. No experimental assignments are available for the 15 other transitions.
On leave from: Departmento de Quimica Física, Universidad de Valencia, Dr. Moliner 50, Burjassot, E-46100-Valencia, Spain 相似文献
12.
Complete active space self-consistent-field (CASSCF) and multiconfigurational second-order perturbation theory (CASPT2) calculations
in conjunction with the ANO-L basis set were performed to investigate systematically the low-lying electronic states of HNCS
and its ions in C
s
symmetry. Our highly accurate calculation indicated that theoretically determined geometric parameters and harmonic vibrational
frequencies for the ground-state X
1A′ are in good agreement with observed experimental data. The geometry of triplet HNCS is clearly favored C
1
symmetry, and the relative energy is predicted to be 3.000 eV (69.2 kcal/mol). The vertical transition energies for the selected
excited states of HNCS were calculated at CASSCF/CASPT2/ANO-L level of theory based on CASSCF optimized geometry. Except for
a few linear states of X
2Π (12A′, 12A″), 14Σ− (14A″), and 12Σ+ (32A′) states of HNCS+, our results confirmed that the majority of excited states are twisted trans-bend structures. The existence of bound excited
anion states has been found for the first time in HNCS−. A more elaborate examination of ionization potential of HNCS (AIP, VIP) than previous reports has been presented. 相似文献
13.
《Chemical physics letters》2001,331(1-2):155-164
The low-lying singlet excited states of CH2BrCl have been calculated using multiconfigurational CASSCF, second-order perturbation theory CASPT2 and its multistate extension MS-CASPT2. The CASSCF method shows spurious valence–Rydberg mixing and a wrong order of states. Inclusion of dynamical correlation by single root CASPT2 lowers dramatically the energy of the valences states but does not lead to a complete separation between valence and Rydberg states. This situation is improved by the MS-CASPT2 calculations, which gives two valence states for both A′ and A″ symmetries below the lowest Rydberg state, corresponding to n(Br)→σ*(C–Br) and n(Cl)→σ*(C–Cl) transitions at 6.1 eV (203 nm) and 7.2 eV (173 nm), and being repulsive along C–Br and C–Cl coordinates. 相似文献
14.
David A. Hrovat Xue-Bin Wang Weston Thatcher Borden 《Journal of computational chemistry》2019,40(1):119-126
(12/12)CASPT2, (16/14)CASPT2, B3LYP, and CCSD(T) calculations have been carried out on 1,8-Naphthoquinone (1,8- NQ ), to predict the low-lying electronic states and their relative energies in this non-Kekulé quinone diradical. CASPT2 predicts a 1A1 ground state, with three other electronic states—3B2, 3B1, and 1B1—within about 10 kcal/mol of the ground state in energy. On the basis of the results of these calculations, it is predicted that NIPES experiments on 1,8- NQ •– will find that 1,8- NQ is a diradical with a singlet ground state. © 2018 Wiley Periodicals, Inc. 相似文献
15.
Johan Lorentzon Per-Åke Malmqvist Markus Fülscher Björn O. Roos 《Theoretical chemistry accounts》1995,91(1-2):91-108
Summary The valence excited states and the 3s, 3p, and 3d (united atom) Rydberg states of benzene and phenol have been obtained by the CASPT2 method, which computes a second-order perturbation correction to complete active space self-consistent field (CASSCF) energies. All non-zero dipole oscillator strengths are also computed, at the CASSCF level. For benzene, 16 singlet and 16 triplet states with excitation energies up to ca. 7.86 eV (63 400 cm–1) are obtained. Of these, 12 singlet and three triplet energies are experimentally known well enough to allow meaningful comparison. The average error is around 0.1 eV. The highest of these singlet states (21 E2g) is the highest valence * state predicted by elementary -electron theory. Its energy is then considerably lower than has been suggested from laser flash experiments, but in perfect agreement with a reinterpretation of that experiment. For phenol, 27 singlet states are obtained, in the range 4.53–7.84 eV (63 300 cm–1). Only the lowest has a well-known experimental energy, which agrees with the computed result within 0.03 eV. The ionization energy is in error by 0.05 eV. 相似文献
16.
We report a series of quantum-chemical calculations for the ground and some of the low-lying excited states of an isolated LiYb molecule by the spin-orbit multistate complete active space second-order perturbation theory (SO-MS-CASPT2). Potential energy curves, spectroscopic constants, and transition dipole moments (TDMs) at both spin-free and spin-orbit levels are obtained. Large spin-orbit effects especially in the TDMs of the molecular states dissociating to Yb((3)P(0,1,2)) excited states are found. To ensure the reliability of our calculations, we test five types of incremental basis sets and study their effect on the equilibrium distance and dissociation energy of the ground state. We also compare CASPT2 and CCSD(T) results for the ground state spectroscopic constants at the spin-free relativistic level. The discrepancies between the CASPT2 and CCSD(T) results are only 0.01 ? in equilibrium bond distance (R(e)) and 200 cm(-1) in dissociation energy (D(e)). Our CASPT2 calculation in the supermolecular state (R=100 a.u.) with the largest basis set reproduces experimental atomic excitation energies within 3% error. Transition dipole moments of the super molecular state (R=100 a.u.) dissociating to Li((2)P) excited states are quite close to experimental atomic TDMs as compared to the Yb((3)P) and Yb((1)P) excited states. The information obtained from this work would be useful for ultracold photoassociation experiments on LiYb. 相似文献
17.
Density functional theory and multiconfigurational CASPT2 and density matrix renormalization group DMRG-CASPT2 have been employed to study the low-lying states of NbGen−/0/+ (n = 1–3) clusters. With the DMRG-CASPT2 method, the active spaces are extended to a size of 20 orbitals. For most of the states, the CASPT2 relative energies are comparable with the DMRG-CASPT2 results. The leading configuration, bond distances, vibrational frequencies, and relative energies of the low-lying states of these clusters were calculated. The ground states of these clusters were computed to be 3Δ, 4Φ, and 5Φ of NbGe−/0/+; 3A2, 4B1, and 3B1 of cyclic-NbGe2−/0/+; and 1A′, 12A″ and 12A′′ (2E), and 3A″ of tetrahedral-NbGe3−/0/+ isomers. For NbGe cluster, our calculations proposed that the 6∑ is almost degenerate with the 4Φ with the CASPT2 and DMRG-CASPT2 relative energies of 0.05 and 0.06 eV. The adiabatic detachment energies of NbGen− (n = 1–3) clusters were estimated to be 1.46, 1.55, and 2.18 eV by the CASPT2 method. The relevant detachment energies of the anionic ground state and the ionization energies of the neutral ground states are evaluated at the CASPT2 level. 相似文献
18.
A method constructing symmetry-adapted bonded Young tableau bases is proposed, based on the symmetry properties of bonded tableaus and the projection operator associated with a point group. Several examples including the ground states and π excited states of O3−, O3, O3+, and C3− are shown for instruction to construct the symmetrized valence bond (VB) wave function. Excitation energies of transitions from the ground states to π excited states of O3−, C3H5, and C3− are calculated with an optimized symmetrized valence bond wave function in the σ–π separation approximation. Good agreement between the VB and experimental excitation energies is observed. The bonding features of the ground state and the first π excited singlet and triplet states for S3 are discussed according to bonding populations from VB calculations. Both the singlet-biradical and the dipole structures have significant contributions to the ground state X 1A1 of S3, while the excited state 1 1B2 is essentially composed of the dipole structures, and the 1 3B2 excited state is comprised from a triplet-biradical structure. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 1–7, 1998 相似文献
19.
G. Chambaud W. Gabriel T. Schmelz P. Rosmus A. Spielfiedel N. Feautrier 《Theoretical chemistry accounts》1993,87(1-2):5-17
Summary The three-dimensional potential energy functions have been calculated from highly correlated multireference configuration interaction electronic wavefunctions for theX
3
B
1,a
1
A
1, andb
1
B
1 states of the NH
2
+
ion. For the quasi-linear electronic ground state this information and the electric dipole moment functions have been used to calculate spectroscopic constants, line intensities and rotationally resolved absorption spectra. For thea
1
A
1-b
1
B
1 bent/quasi-linear Renner-Teller system ro-vibronic energy levels have been obtained from a variational approach accounting for anharmonicity, rotation-vibration and electronic angular momenta coupling effects. The vibronic levels are given for energies up to 13 500 cm–1 for the bending levels and up to 8000 cm–1 for the stretching and combination levels.Dedicated in the honor of Prof. Werner Kutzelnigg 相似文献
20.
Robert P. Krawczyk Karsten Malsch Georg Hohlneicher Ralph C. Gillen Wolfgang Domcke 《Chemical physics letters》2000,320(5-6)
The potential-energy functions of the 1 1Bu and 2 1Ag excited valence states of trans-butadiene have been characterised by the CASPT2 method. Based on these ab initio data, a vibronic-coupling model describing the conical intersection of the 1 1Bu and 2 1Ag states has been constructed. UV resonance-Raman and absorption spectra have been calculated, employing the time-dependent approach. The time-dependent wave-packet calculations reproduce the expected ultrafast (≈30 fs) radiationless decay of the optically bright 1 1Bu state into the dark 2 1Ag state. 相似文献