共查询到20条相似文献,搜索用时 31 毫秒
1.
Christopher Robertson Jesús González-Vázquez Ines Corral Sergio Díaz-Tendero Cristina Díaz 《Journal of computational chemistry》2019,40(6):794-810
The presence of nonadiabatic effects during the interaction of small molecules with metals has been observed experimentally for the last decades. Specially remarkable are the effects found for NO/Au, where experiments have suggested the presence of very strong vibronic coupling during the molecular scattering. However, the accurate inclusion of the nonadiabatic effects in periodic boundary conditions (PBC) theoretical methods remain an unapproachable challenge. Here, aiming to give some theoretical insight to the strong vibronic coupling, we have adopted a pragmatic point of view, taking use of an auxiliary simplified system, NO/Au3. We show the importance of nonadiabatic coupling, during the scattering of NO from a Au3 cluster, using a diabatic representation of 12 electronic states of the system, including a few charge-transfer states. Our diabatic representation is obtained by rotating the orbital and configuration interaction (CI) vectors of a restricted active space (RAS) wavefunction. We present a strategy for extracting the best effective manifold of states relevant to the system, below some prescribed energy, directly from the RAS CI vectors. This scheme is able to disentangle a large dense manifold of adiabatic states with strong coupling and crossings. This approach is also shown to work for multireference configuration interaction (MRCI). By performing quantum propagations, we observed an increase in vibrational redistribution with increasing initial vibrational or translational energies. We suggest that these nonadiabatic effects should also be present at smaller energies in larger clusters. © 2018 Wiley Periodicals, Inc. 相似文献
2.
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
3.
María Luz Hernndez Jos María Alvario Antonio Lagan Marzio Rosi Antonio Sgamellotti 《International journal of quantum chemistry》2002,86(1):79-89
The lowest singlet 11A′ and 11A″ potential energy surfaces (PES) of the O(1D)+HBr system have been ab initio computed. The complete active space self‐consistent field (CASSCF) method was used in most of the calculations, considering all the valence orbitals as active. The calculations were complemented with both analytical gradient calculations to characterize the stationary points and multireference configuration interaction (MRCI) calculations at selected nuclear geometries to improve the determination of the barrier heights and of the energetics. Electronic energy values for both PESs were then independently fitted by polynomial expansions in bond order coordinates. On the fitted surfaces quasi‐classical trajectories were separately run. Single‐surface calculations behave qualitatively different for the ground and the excited PES at low collision energies. A satisfactory agreement with existing experimental data was obtained by using the ground PES while calculations performed on the excited 11A″ PES worsened the agreement. However, when collision energy is increased, detailed experimental distributions are less well reproduced by calculations on the ground PES. This may imply the participation via nonadiabatic transitions of the 21A′ PES at higher energies while the adiabatic ground singlet PES well describes reactive scattering at low collision energy. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 相似文献
4.
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
5.
We used multiconfiguration quasidegenerate perturbation theory and the fourfold-way direct diabatization scheme to calculate ab initio potential-energy surfaces at 3600 nuclear geometries of NH3. The calculations yield the adiabatic and diabatic potential-energy surfaces for the ground and first electronically excited singlet states and also the diabatic coupling surfaces. The diabatic surfaces and coupling were fitted analytically to functional forms to obtain a permutationally invariant 2 x 2 diabatic potential-energy matrix. An analytic representation of the adiabatic potential-energy surfaces is then obtained by diagonalizing the diabatic potential-energy matrix. The analytic representation of the surfaces gives an analytic representation of the four-dimensional conical intersection seam which is discussed in detail. 相似文献
6.
A theory of vibronic coupling in molecules is presented and applied to butatriene. The energies and coupling constants which enter the calculation are computed using ab initio Hartree—Fock and many-body methods. The influence of the energy splitting and the coupling constants on the calculated spectrum is discussed. It is definitely shown that the “mystery band” in the photoelectron spectrum of butatriene arises from the vibronic coupling between the electronic states 2B3g and 2B3u. To reproduce the experimental observations it is essential to include in the calculation both totally and non-totally symmetric vibrational modes. 相似文献
7.
M. Perić S. D. Peyerimhoff R. J. Buenker 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,24(2):177-198
A purely ab initio study of the vibronic structure of the C2H spectrum in the region up to 7000 cm?1, which is complicated by the coupling of theX 2Σ+ andA 2 II systems, is presented. The potential surfaces for the three lowest-lying electronic states 12 A′, 22 A′ and 12 A″ correlating withX 2Σ+ andA 2 II at the linear molecular geometry are calculated for the various geometrical distortions by means of the multireference configuration interaction (MRD-CI) method. These adiabatic surfaces are transformed into suitable diabatic counterparts. An approach is developed for a simultaneous treatment of three electronic states coupled via the bending and C-C stretching vibrations. Spin-orbit splitting of the vibronic levels and the vibronically averaged values for the hyperfine coupling constants are computed. The results obtained in this study enable a reliable explanation of the available experimental findings of the C2H spectrum and predict a number of features to be verified by future experiments. 相似文献
8.
The electronic structures of the ground and excited states of ketene imine (HHCCNH) have been studied by ab initio SCF and CI calculations. The nucleophilic nature of the β carbon with respect to nitrogen has been discussed using calculated electrostatic potentials and by calculated energy differences between the parent and protonated species. The electronically excited 1A″ and 3A″ states are found to be almost degenerate. 相似文献
9.
The ground state and some lowest excited states of ozone are calculated by the semiempirical MNDO method using configuration
interaction to explain the Wulf absorption band and photodissociation of ozone. The results of calculations show that3A2(13A′’) is the lowest excited triplet state of O3; a transition to this state from the ground X1 A1 state is responsible for the weak Wulf absorption. The oscillator strength (f = 3.2·10-7) and the radiative lifetime of the A2 state (Τ = 0.01 s) are in agreement with recent ab initio calculations.
Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 6, pp. 1067–1073, November–December, 1997. 相似文献
10.
N. S. Golubev P. M. Tolstoi D. N. Shchepkin 《Russian Journal of General Chemistry》2006,76(8):1183-1190
A nonadiabatic correction to the H/D isotope effect on the constant of electronic magnetic shielding of a nucleus was estimated within the framework of the first-order perturbation theory. The procedure consists in the ab initio calculation of frequencies and relative intensities in the vibronic spectrum for H and D forms of a molecule taking into account only the transitions allowed in the magnetic-dipole approximation. With the elementary assumptions (case of Herzberg vibronic interaction), the semiquantitative estimation of adiabatic (geometrical) and nonadiabatic contributions to the H/D isotope effect on the 15N shielding constant of a complex with the HF-pyridine hydrogen bond was carried out. These two contributions to the isotope effect are comparable in the order of magnitude, at least for unsaturated molecules with low-lying excited electronic states. A correct solution to the problem requires ab initio calculation that is not based on the Born-Oppenheimer approximation. 相似文献
11.
《Chemical physics》1986,105(3):471-479
Time-resolved sub-Doppler laser spectroscopy under collision-free conditions in a supersonic NO2 beam has proved that selectively excited rovibronic levels show only pure exponential decays with lifetimes from 40 to 100 μs depending on the strength of their coupling to non-radiative levels. These measurements support earlier results which can be explained by vibronic and spin-orbit coupling between levels in the 2B2 and X2A1 states. 相似文献
12.
Tae-Kyu Ha 《Chemical physics letters》1978,57(1):64-70
An ab initio SCF and CI study has been carried out for the ground and electronically excited states of biacetyl (CH3COCOCH3). The second absorption band in the 4.40 eV region has been assigned to a 1Ag → 1Bg nπ* transition The character of the lower-lying states has been analyzed in terms of the CI wavefunctions. 相似文献
13.
A simple technique of scaling two-electron integrals in ab initio calculations of the electronically excited states of transition
metal complexes is proposed. This technique uses the fact that one-center two-electron integrals depend linearly on the scaling
factor when Slater type functions are subjected to scaling transformation. This leads to a linear dependence of the d—d transition
energy on the “scale” of Coulomb interaction, which allows one to affect the calculation result by varying the Slater exponential.
To test the technique, ab initio configuration interaction and full active space calculations of the low excited states of
the CrF
6
3-
, MnF
6
2-
, and VF
6
3-
complexes are performed. For transition elements, a basis of Slater type effective functions chosen from the optical spectra
of the atoms and ions of transition elements is used. It is shown that in the STO-6G basis with effective exponentials, experimental
transitions are reproduced with an accuracy of about 2000 cm-1 even with the use of small active space determined by the orbitals localized on the central atom of the complex. 相似文献
14.
LCGTO-LSD calculations for ground (3B1) and excited (1A1) states of methylene, CH2, have been performed. Various exchange-correlation potentials and a variety of basis sets (including f functions) have been used. For both states the LSD optimized geometry agrees well with both experimental and the most advanced ab initio results. The correct ground state is found, and the 1A1-3B1 energy separation was found to be ~ 15 kcal/mol, using the “best” local exchange-correlation potential (VWN ), the experimental value being ~ 9 kcal/mol. This result compares favorably with the Hartree-Fock limit separation of 25 kcal/mol. The Kohn-Sham exchange potential leads to a gap of ~26 kcal/mol. 相似文献
15.
Gromov EV Trofimov AB Vitkovskaya NM Köppel H Schirmer J Meyer HD Cederbaum LS 《The Journal of chemical physics》2004,121(10):4585-4598
The excitation spectra and molecular dynamics of furan associated with its low-lying excited singlet states 1A2(3s), 1B2(V), 1A1(V'), and 1B1(3p) are investigated using an ab initio quantum-dynamical approach. The ab initio results of our previous work [J. Chem. Phys. 119, 737 (2003)] on the potential energy surfaces (PES) of these states indicate that they are vibronically coupled with each other and subject to conical intersections. This should give rise to complex nonadiabatic nuclear dynamics. In the present work the dynamical problem is treated using adequate vibronic coupling models accounting for up to four coupled PES and thirteen vibrational degrees of freedom. The calculations were performed using the multiconfiguration time-dependent Hartree method for wave-packet propagation. It is found that in the low-energy region the nuclear dynamics of furan is governed mainly by vibronic coupling of the 1A2(3s) and 1B2(V) states, involving also the 1A1(V') state. These interactions are responsible for the ultrafast internal conversion from the 1B2(V) state, characterized by a transfer of the electronic population to the 1A2(3s) state on a time scale of approximately 25 fs. The calculated photoabsorption spectrum of furan is in good qualitative agreement with experimental data. Some assignments of the measured spectrum are proposed. 相似文献
16.
Laurentius Windholz Gerald Zerza Goran Pichler Bernd Heß 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,18(4):373-377
Visible argon ion laser lines were used to induce the chemiluminescence of the NaHg excimer. Sodium dimers, excited into theB 1Π u state, produced in reactive collision with Hg atoms the NaHg excimers in the first excited electronic states. A qualitative analysis of the origin of the observed spectra, based on ab initio NaHg potential curves calculations, is presented. 相似文献
17.
Mark S. Gordon 《Chemical physics letters》1976,44(3):507-511
STO 4G calculations are carried out on methane in both tetrahedral and Jahn—Teller distorted C2v and C3v symmetries. Large increases in CH bond lengths are predicted in all states, and the IB1 state in C2v symmetry is predicted to dissociate to IB1 methylene and 1A1 H2 width no energy barrier. THe results are compared with earlier INDO calculations, and the latter are found to qualitatively consistent with the ab initio results. 相似文献
18.
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
19.
The two-photon excitation spectrum 1B2u ← 1Ag of p-difluorobenzene in the gas phase is presented and analysed. The normal absorption is electric dipole allowed and shows no vibronic coupling, but the two-photon absorption is electric dipole forbidden and displays rich vibronic structure. Eight vibronic origins are assigned to their excited state fundamentals by analysis of the hot bands and by analogy with benzene. The only previously unassigned ground state frequency, an au mode, is active in the spectrum and is accordingly assigned. The sequences and the abundant Fermi resonances accompanying absorption are also partially assigned. 相似文献
20.
Self-consistent ab initio generalized valence bond (GVB) and configuration interaction (Cl) calculations are presented for the ground and valence electronic excited states of trans-1,3-butadine and all trans-1,3,5-hexatrine. Previous workers have suggested that (all trans) polyenes exhibit a parity-forbidden valence excited state (21 Ag at an energy just below that of the first dipole-allowed (11 Bu) state. We find such valence excited electronic states for butadiene (ΔE = 7.06 eV) and hexatriene (ΔE = 5.87 eV), but in both cases the excitation energy is considerably higher than the dipole-allowed transitions (zero-zero transitions at 5.95 eV and 4.95 eV, respectively). The lower two triplet states are found at 3.35 eV and 5.08 eV for butadie and at 2.71 eV and 4.32 eV in hexatrine, in good agreement with experimental values (3.2–3.3 eV and 4.92 eV for butadiene and 2.66 eV and 4.1–4.2 eV for hexatrine). Considering the states formed by removing one electron from the π space we found ion states at 8.95 eV and 11.40 eV for butadiene and at 8.33 eV, 10.53 eV, and 11.60 eV for hexatriene, in godo agreement with experimental results (9.0 eV and 11.5 eV for butadiene and 8.45 eV, 10.43 eV and 11.6 eV for hexatriene). 相似文献