Direct construction of diabatic states in the CASSCF approach. Application to the conical intersection of the 1A2 and 1B1 excited states of ozone

Domcke, Wolfgang; Woywod, Clemens

doi:10.1016/0009-2614(93)90110-m

Cited by 154 publications

(141 citation statements)

References 36 publications

Supporting

Mentioning

140

Contrasting

Order By: Relevance

“…Recent work by ourselves [1][2][3]10] and others [11,12] has shown that the block diagonalization method provides a very powerful technique to determine the necessary dissociating, autoionizing states and coupling terms for N 2 H. The principal difficulty that one encounters when trying to calculate the dissociating surface using the standard techniques of electronic structure is that the states of interest are (1) highly excited and (2) strongly mixed with other states. Multiple curve crossings occur, and it can be very difficult to isolate the desired potential surface.…”

Section: Determination Of Autoionizing States Using Block Diagonalizamentioning

confidence: 99%

Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

Kashinski

Talbi

Hickman

2015

EPJ Web of Conferences

View full text Add to dashboard Cite

Abstract. We describe our implementation of the block diagonalization method for calculating the potential surfaces necessary to treat dissociative recombination (DR) of electrons with N 2 H + . Using the methodology we have developed over the past few years, we performed multi-reference, configuration interaction calculations for N 2 H + and N 2 H with a large active space using the GAMESS electronic structure code. We treated both linear and bent geometries of the molecules, with N 2 fixed at its equilibrium separation. Because of the strong Rydberg-valence coupling in N 2 H, it is essential to isolate the appropriate dissociating, autoionizing states. Our procedure requires only modest additional effort beyond the standard methodology. The results indicate that the crossing between the dissociating neutral curve and the initial ion potential is not favorably located for DR, even if the molecule bends. The present calculations thereby confirm our earlier results for linear N 2 H and reinforce the conclusion that the direct mechanism for DR is likely to be inefficient. We also describe interesting features of our preliminary calculations on SH.

show abstract

Section: Determination Of Autoionizing States Using Block Diagonalizamentioning

confidence: 99%

Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

Kashinski

Talbi

Hickman

2015

EPJ Web of Conferences

View full text Add to dashboard Cite

show abstract

“…From a first-principles investigation of the photodissociation on the Chappuis band of ozone, Woywod et al 47 applied a method 23,24 for obtaining smoothly varying complete-active-space self-consistent-field (CASSCF) wave functions by employing MO theory with nearly constant linear combination of atomic orbital (LCAO) coefficients, followed by block-diagonalization 27 of the Hamiltonian, to obtain slowly varying configuration interaction (CI) coefficients. By interpolating the resulting diabatic points, 47 they were able to achieve highly non-varying diagonal diabatic representations for the 1 1 A′′/2 1 A′′ states of O 3 , which have been subsequently employed in dynamics calculations.…”

Section: Global Multisheeted Approaches Employing Diabatization Schemmentioning

confidence: 99%

HN₂(²A‘) Electronic Manifold. II. Ab Initio Based Double-Sheeted DMBE Potential Energy Surface via a Global Diabatization Angle

Mota

Varandas

2008

J. Phys. Chem. A

View full text Add to dashboard Cite

A double-sheeted double many-body expansion potential energy surface is reported for the coupled 1 2 A′/ 2 2 A′ states of HN 2 by fitting about 6000 ab initio energies. All crossing seams are described to their full extent on the basis of converged results. The lowest adiabatic sheet is fitted with a rmsd of 0.8 kcal mol -1 with respect to the calculated energies up to 100 kcal mol -1 above the absolute minimum, and the topology of the first excited-state investigated with the aid of the upper adiabatic sheet. A new scheme that overcomes obstacles in previous diabatization methods for modeling global double-sheeted potential energy surfaces is also reported. The novel approach uses a global diabatization angle which allows the diabats to mimic both the crossing seams and atom-diatom dissociation limits.

show abstract

“…In such regions we require the fourth element, which involves maximizing the overlap of one orbital with a reference molecular orbital. The fourfold way is effective at producing diabatic orbitals even in cases where a maximum overlap criterion 35 applied to all orbitals fails. The resulting diabatic orbitals are globally defined and unique (pathindependent) if the dominant configurations and weak coupling regions can be defined unambiguously.…”

Section: General Theoretical Considerations and Definitionsmentioning

confidence: 99%

Introductory lecture: Nonadiabatic effects in chemical dynamics

et al. 2004

View full text Add to dashboard Cite

Recent progress in the theoretical treatment of electronically nonadiabatic processes is discussed. First we discuss the generalized Born-Oppenheimer approximation, which identifies a subset of strongly coupled states, and the relative advantages and disadvantages of adiabatic and diabatic representations of the coupled surfaces and their interactions are considered. Ab initio diabatic representations that do not require tracking geometric phases or calculating singular nonadiabatic nuclear momentum coupling will be presented as one promising approach for characterizing the coupled electronic states of polyatomic photochemical systems. Such representations can be accomplished by methods based on functionals of the adiabatic electronic density matrix and the identification of reference orbitals for use in an overlap criterion. Next, four approaches to calculating or modeling electronically nonadiabatic dynamics are discussed: (1) accurate quantum mechanical scattering calculations, (2) approximate wave packet methods, (3) surface hopping, and (4) self-consistent-potential semiclassical approaches. The last two of these are particularly useful for polyatomic photochemistry, and recent refinements of these approaches will be discussed. For example, considerable progress has been achieved in making the surface hopping method more applicable to the study of systems with weakly coupled electronic states. This includes introducing uncertainty principle considerations to alleviate the problem of classically forbidden surface hops and the development of an efficient sampling algorithm for low-probability events. A topic whose central importance in a number of quantum mechanical fields is becoming more widely appreciated is the introduction of decoherence into the quantal degrees of freedom to account for the effect of the classical treatment on the other degrees of freedom, and we discuss how the introduction of such decoherence into a self-consistent-potential approximation leads to a reasonably accurate but very practical trajectory method for electronically nonadiabatic processes. Finally, the performances of several dynamical methods for Landau-Zener-type and Rosen-Zener-Demkov-type reactive scattering problems are compared.

show abstract

Direct construction of diabatic states in the CASSCF approach. Application to the conical intersection of the 1A2 and 1B1 excited states of ozone

Cited by 154 publications

References 36 publications

Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

HN₂(²A‘) Electronic Manifold. II. Ab Initio Based Double-Sheeted DMBE Potential Energy Surface via a Global Diabatization Angle

Introductory lecture: Nonadiabatic effects in chemical dynamics

Contact Info

Product

Resources

About

Direct construction of diabatic states in the CASSCF approach. Application to the conical intersection of the 1A2 and 1B1 excited states of ozone

Cited by 154 publications

References 36 publications

Using block diagonalization to determine dissociating autoionizing states: Application to N2H, and the outlook for SH

Using block diagonalization to determine dissociating autoionizing states: Application to N2H, and the outlook for SH

HN2(2A‘) Electronic Manifold. II. Ab Initio Based Double-Sheeted DMBE Potential Energy Surface via a Global Diabatization Angle

Introductory lecture: Nonadiabatic effects in chemical dynamics

Contact Info

Product

Resources

About

Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

HN₂(²A‘) Electronic Manifold. II. Ab Initio Based Double-Sheeted DMBE Potential Energy Surface via a Global Diabatization Angle