共查询到20条相似文献，搜索用时 15 毫秒
1.
Neethu Anand Sai Vamsi Krishna Isukapalli Sivaranjana Reddy Vennapusa 《Journal of computational chemistry》2020,41(11):1068-1080
Nonradiative decay pathways associated with vibronically coupled S1(ππ*)–S2(nπ*) potential energy surfaces of 3- and 5-hydroxychromones are investigated by employing the linear vibronic coupling approach. The presence of a conical intersection close to the Franck–Condon point is identified based on the critical examination of computed energetics and structural parameters of stationary points. We show that very minimal displacements of relevant atoms of intramolecular proton transfer geometry are adequate to drive the molecule toward the conical intersection nuclear configuration. The evolving wavepacket on S1(ππ*) bifurcates at the conical intersection: a part of the wavepacket moves to S2(nπ*) within a few femtoseconds while the other decays to S1 minimum. Our findings indicate the possibility of forming the proton transfer tautomer product via S2(nπ*), competing with the traditional pathway occurring on S1(ππ*). 相似文献
2.
锥形交叉可以通过几何相效应影响核动力学.在过去的一些年里关于锥形交叉的理论有大量的发展和进步,本文综述了分子反应动力学领域针对几何相效应研究的一些理论成果.介绍了分子反应动力学中与几何相效应直接相关的一些最新成果,同时也对这些重要结果进行了解释.我们相信几何相效应将会在非绝热化学中发挥最重要的作用. 相似文献
3.
Reaction dynamics of prototypical, D + H2 and Cl (2P) + H2, chemical reactions occurring through the conical intersections of the respective coupled multi-sheeted potential energy
surfaces is examined here. In addition to the electronic coupling, nonadiabatic effects due to relativistic spin-orbit coupling
are also considered for the latter reaction. A time-dependent wave packet propagation approach is undertaken and the quantum
dynamical observables viz., energy resolved reaction probabilities, integral reaction cross-sections and thermal rate constants
are reported. 相似文献
4.
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
5.
James A. Green Martha Yaghoubi Jouybari Daniel Aranda Roberto Improta Fabrizio Santoro 《Molecules (Basel, Switzerland)》2021,26(6)
We have recently proposed a protocol for Quantum Dynamics (QD) calculations, which is based on a parameterisation of Linear Vibronic Coupling (LVC) Hamiltonians with Time Dependent (TD) Density Functional Theory (TD-DFT), and exploits the latest developments in multiconfigurational TD-Hartree methods for an effective wave packet propagation. In this contribution we explore the potentialities of this approach to compute nonadiabatic vibronic spectra and ultrafast dynamics, by applying it to the five nucleobases present in DNA and RNA. For all of them we computed the absorption spectra and the dynamics of ultrafast internal conversion (100 fs timescale), fully coupling the first 2–3 bright states and all the close by dark states, for a total of 6–9 states, and including all the normal coordinates. We adopted two different functionals, CAM-B3LYP and PBE0, and tested the effect of the basis set. Computed spectra are in good agreement with the available experimental data, remarkably improving over pure electronic computations, but also with respect to vibronic spectra obtained neglecting inter-state couplings. Our QD simulations indicate an effective population transfer from the lowest energy bright excited states to the close-lying dark excited states for uracil, thymine and adenine. Dynamics from higher-energy states show an ultrafast depopulation toward the more stable ones. The proposed protocol is sufficiently general and automatic to promise to become useful for widespread applications. 相似文献
6.
Dr. Ya‐Ting Wang Dr. Xiang‐Yang Liu Prof. Dr. Ganglong Cui Prof. Dr. Wei‐Hai Fang Prof. Dr. Walter Thiel 《Angewandte Chemie (International ed. in English)》2016,55(45):14009-14013
Electronic structure calculations and nonadiabatic dynamics simulations (more than 2000 trajectories) are used to explore the Z–E photoisomerization mechanism and excited‐state decay dynamics of two arylazopyrazole photoswitches. Two chiral S1/S0 conical intersections with associated enantiomeric S1 relaxation paths that are barrierless and efficient (timescale of ca. 50 fs) were found. For the parent arylazopyrazole (Z8) both paths contribute evenly to the S1 excited‐state decay, whereas for the dimethyl derivative (Z11) each of the two chiral cis minima decays almost exclusively through one specific enantiomeric S1 relaxation path. To our knowledge, the Z11 arylazopyrazole is thus the first example for nearly stereospecific unidirectional excited‐state relaxation. 相似文献
7.
Michael Baer Alexander M. Mebel Gert D. Billing 《International journal of quantum chemistry》2002,90(6):1577-1585
The idea to derive the nonadiabatic coupling terms by solving the Curl equations (Avery, J.; Baer, M.; Billing, G. D. Mol Phys 2002, 100, 1011) is extended to a three‐state system where the first and second states form one conical intersection, i.e., τ12 and the second and the third states form another conical intersection, i.e., τ23. Whereas the two‐state Curl equations form a set of linear differential equations, the extension to a three‐state system not only increases the number of equations but also leads to nonlinear terms. In the present study, we developed a perturbative scheme, which guarantees convergence if the overlap between the two interacting conical intersections is not too strong. Among other things, we also revealed that the nonadiabatic coupling term between the first and third states, i.e., τ13 (such interactions do not originate from conical intersection) is formed due to the interaction between τ12 and τ23. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
8.
Dr. Shu‐Hua Xia Prof. Dr. Ganglong Cui Prof. Dr. Wei‐Hai Fang Prof. Dr. Walter Thiel 《Angewandte Chemie (International ed. in English)》2016,55(6):2067-2072
Photoswitchable azobenzene cross‐linkers can control the folding and unfolding of peptides by photoisomerization and can thus regulate peptide affinities and enzyme activities. Using quantum mechanics/molecular mechanics (QM/MM) methods and classical MM force fields, we report the first molecular dynamics simulations of the photoinduced folding and unfolding processes in the azobenzene cross‐linked FK‐11 peptide. We find that the interactions between the peptide and the azobenzene cross‐linker are crucial for controlling the evolution of the secondary structure of the peptide and responsible for accelerating the folding and unfolding events. They also modify the photoisomerization mechanism of the azobenzene cross‐linker compared with the situation in vacuo or in solution. 相似文献
9.
Vaibhav Singh Hugo A. Lpez Pea Jacob M. Shusterman Patricia Vindel-Zandbergen Katharine Moore Tibbetts Spiridoula Matsika 《Molecules (Basel, Switzerland)》2022,27(7)
The dynamics of the dimethyl methylphosphonate (DMMP) radical cation after production by strong field adiabatic ionization have been investigated. Pump-probe experiments using strong field 1300 nm pulses to adiabatically ionize DMMP and a 800 nm non-ionizing probe induce coherent oscillations of the parent ion yield with a period of about 45 fs. The yields of two fragments, PO2C2H7+ and PO2CH4+, oscillate approximately out of phase with the parent ion, but with a slight phase shift relative to each other. We use electronic structure theory and nonadiabatic surface hopping dynamics to understand the underlying dynamics. The results show that while the cation oscillates on the ground state along the P=O bond stretch coordinate, the probe excites population to higher electronic states that can lead to fragments PO2C2H7+ and PO2CH4+. The computational results combined with the experimental observations indicate that the two conformers of DMMP that are populated under experimental conditions exhibit different dynamics after being excited to the higher electronic states of the cation leading to different dissociation products. These results highlight the potential usefulness of these pump-probe measurements as a tool to study conformer-specific dynamics in molecules of biological interest. 相似文献
10.
Chemical groups are known to tune the luminescent efficiencies of graphene-related nanomaterials, but some species, including the epoxide group (−COC−), are suspected to act as emission-quenching sites. Herein, by performing nonadiabatic excited-state dynamics simulations, we reveal a fast (within 300 fs) nonradiative excited-state decay of a graphene epoxide nanostructure from the lowest excited singlet (S1) state to the ground (S0) state via a conical intersection (CI), at which the energy difference between the S1 and S0 states is approximately zero. This CI is induced after breaking one C−O bond at the −COC− moiety during excited-state structural relaxation. This study ascertains the role of epoxide groups in inducing the nonradiative recombination of the excited electron-hole, providing important insights into the CI-promoted nonradiative de-excitations and the luminescence tuning of relevant materials. In addition, it shows the feasibility of utilizing nonadiabatic excited-state dynamics simulations to investigate the photophysical processes of the excited states of graphene nanomaterials. 相似文献
11.
The effects of magnetic exchange, double exchange and vibronic coupling on magnetic properties of the d1–d1–d2 trimer with C2V symmetry are discussed in the generalized vibronic model. The magnetic moments are calculated with the semiclassical adiabatic approach. The results show that the PKS vibronic coupling and the P vibronic coupling favor the localization and the delocalization of the ‘extra’ electron, respectively. The magnetic properties are determined by the interplay among magnetic exchange, double exchange and vibronic coupling. 相似文献
12.
Jacopo Fregoni Stefano Corni Maurizio Persico Giovanni Granucci 《Journal of computational chemistry》2020,41(23):2033-2044
13.
Studying the excited-state decay process is crucial for materials research because what happens to the excited states determines how effective the materials are for many applications, such as photoluminescence and photocatalysis. The high computational cost, however, limits the use of high-accuracy theoretical approaches for analyzing research systems containing a significant number of atoms. Time-dependent density functional theory is a practical approach to investigate the photorelaxation processes in these systems, as demonstrated in the studies of the excited-state decays of heptazine-water clusters and adenine in water described in this review. Here, we highlight the importance of conical intersections in the excited-state decay processes of these systems using the aforementioned examples. In the heptazine-water and adenine-water systems, these intersections are associated with the photocatalytic water splitting reaction, caused by a barrierless reaction called water to adenine electron-driven proton transfer. We expect the result would be helpful for researching the excited-state decays of graphitic carbon nitride materials and DNA nucleotides. 相似文献
14.
The effect of magnetic exchange, double exchange, vibronic coupling, and asymmetry on magnetic properties of d2–d3 systems is discussed. The temperature‐dependent magnetic moment was calculated with the semiclassical adiabatic approach. The results show that the vibronic coupling from the out‐of‐phase breathing vibration on the metal sites (Piepho, Krausz, and Schatz [PKS] model) and the vibronic coupling from the stretching vibration between the metal sites (P model) favor the localization and delocalization of the “extra” electron in mixed‐valence dimers, respectively. The magnetic properties are determined by the interplay among magnetic exchange, double exchange, and vibronic coupling. The results obtained by analyzing d2–d3 systems can be generalized to other full delocalized dinuclear mixed valence systems with a unique transferable electron. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
15.
非绝热动力学普遍存在于光物理和光化学过程中。描述非绝热跃迁需要处理电子-原子核间的相互耦合运动。由于计算量随体系尺度增大剧烈增长,准确的量子动力学计算目前只适用于描述小分子体系。为了研究多原子分子体系的非绝热过程,近年来发展了一些基于量子-经典动力学近似方法。本文将对典型的这类方法包括经典Ehrenfest方法、面跳跃方法、基于Wigner表示的混合量子-经典方法进行简要的介绍,并讨论如何将量子-经典动力学方法与电子结构从头算手段相结合,模拟非绝热过程。重点阐明各种方法的基本思想和优缺点,并对该领域的发展进行展望。 相似文献
16.
17.
The photodetachment spectroscopy of B3- anion is theoretically studied with the aid of a quantum dynamical approach. The theoretical results are compared with the available experimental photoelectron spectra of B3-. Both B3- and B3 possess D(3h) symmetry at the equilibrium configuration of their electronic ground state. Distortion of B3 along its degenerate vibrational mode nu2 splits the degeneracy of its excited C2E' electronic manifold and exhibits (E [symbol: see text] e)-Jahn-Teller (JT) activity. The components of the JT split potential energy surface form conical intersections, and they can also undergo pseudo-Jahn-Teller (PJT) crossings with the X2A1' electronic ground state of B3 via the degenerate nu2 vibrational mode. The impact of the JT and PJT interactions on the nuclear dynamics of B3 in its X2A1'-C2E' electronic states is examined here by establishing a diabatic model Hamiltonian. The parameters of the electronic part of this Hamiltonian are calculated by performing electronic structure calculations and the nuclear dynamics on it is simulated by solving quantum eigenvalue equation. The theoretical results are in good accord with the experimental data. 相似文献
18.
In the present work, we have studied modifications in the transition and permanent dipole moments of states in a coupled basis (including vibronic coupling) due to variations in the transition dipole moment between the uncoupled states, m12, as a function of the parameter δ = 0/ω0 (relative aperture) of the potential‐energy curves of the states involved. Modifications in the slopes of the transition and permanent dipole moments of the coupled states and changes in the magnitude of maximal intensity of the four‐wave mixing (FWM) signal are observed due to variations in these parameters. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
19.
LiLing Wang Alireza Azizi Roya Momen Tianlv Xu Steven R. Kirk Michael Filatov Samantha Jenkins 《International journal of quantum chemistry》2020,120(1):e26062
Next-generation quantum theory of atoms in molecules was applied to analyze, along an entire bond path, intramolecular interactions known to influence the photoisomerization dynamics of a light-driven rotary molecular motor. The 3D bond-path framework set B0,1 constructed from the least and most preferred directions of electronic motion, provided new insights into the bonding leading to different S1 state lifetimes including the first quantification of covalent character of a closed-shell intramolecular bond path. We undertook the first use of the stress tensor trajectory Tσ(s) analysis on selected nonadiabatic molecular dynamics trajectories with the electron densities obtained using the ensemble density functional theory method. The stress tensor Tσ(s) analysis was found to be well suited to follow the dynamics trajectories that included the S0 and S1 electronic states through the conical intersection and also provided to a new measure to assess the degree of purity of the axial bond rotation for the design of rotary molecular motors. 相似文献
20.
Milena Shahu 《International journal of quantum chemistry》2006,106(2):501-506
A theoretical study has been carried out on the allyl radical in its ground and first excited electronic states. Complete active space self‐consistent field (CASSCF) calculations show the presence of a conical intersection between the ground and first excited electronic states (～400 cm?1 above the adiabatic excited state energy), reached by decreasing the C? C? C angle and twisting the C? C bonds. The presence of this conical intersection provides a likely explanation for the very rapid predissociation in the excited electronic state. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献