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Title: Quasi-diabatic States from Active Space Decomposition

 [1];  [1]
  1. Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208, United States
Publication Date:
Sponsoring Org.:
OSTI Identifier:
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Resource Type:
Journal Article: Published Article
Journal Name:
Journal of Chemical Theory and Computation
Additional Journal Information:
Journal Volume: 10; Journal Issue: 9; Related Information: CHORUS Timestamp: 2017-12-05 08:56:53; Journal ID: ISSN 1549-9618
American Chemical Society
Country of Publication:
United States

Citation Formats

Parker, Shane M., and Shiozaki, Toru. Quasi-diabatic States from Active Space Decomposition. United States: N. p., 2014. Web. doi:10.1021/ct5004753.
Parker, Shane M., & Shiozaki, Toru. Quasi-diabatic States from Active Space Decomposition. United States. doi:10.1021/ct5004753.
Parker, Shane M., and Shiozaki, Toru. Wed . "Quasi-diabatic States from Active Space Decomposition". United States. doi:10.1021/ct5004753.
title = {Quasi-diabatic States from Active Space Decomposition},
author = {Parker, Shane M. and Shiozaki, Toru},
abstractNote = {},
doi = {10.1021/ct5004753},
journal = {Journal of Chemical Theory and Computation},
number = 9,
volume = 10,
place = {United States},
year = {Wed Jul 23 00:00:00 EDT 2014},
month = {Wed Jul 23 00:00:00 EDT 2014}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/ct5004753

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Cited by: 14works
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Web of Science

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  • This paper reviews basic results from a theory of the a priori classical probabilities (weights) in state-averaged complete active space self-consistent field (SA-CASSCF) models. It addresses how the classical probabilities limit the invariance of the self-consistency condition to transformations of the complete active space configuration interaction (CAS-CI) problem. Such transformations are of interest for choosing representations of the SA-CASSCF solution that are diabatic with respect to some interaction. I achieve the known result that a SA-CASSCF can be self-consistently transformed only within degenerate subspaces of the CAS-CI ensemble density matrix. For uniformly distributed (“microcanonical”) SA-CASSCF ensembles, self-consistency is invariant tomore » any unitary CAS-CI transformation that acts locally on the ensemble support. Most SA-CASSCF applications in current literature are microcanonical. A problem with microcanonical SA-CASSCF models for problems with “more diabatic than adiabatic” states is described. The problem is that not all diabatic energies and couplings are self-consistently resolvable. A canonical-ensemble SA-CASSCF strategy is proposed to solve the problem. For canonical-ensemble SA-CASSCF, the equilibrated ensemble is a Boltzmann density matrix parametrized by its own CAS-CI Hamiltonian and a Lagrange multiplier acting as an inverse “temperature,” unrelated to the physical temperature. Like the convergence criterion for microcanonical-ensemble SA-CASSCF, the equilibration condition for canonical-ensemble SA-CASSCF is invariant to transformations that act locally on the ensemble CAS-CI density matrix. The advantage of a canonical-ensemble description is that more adiabatic states can be included in the support of the ensemble without running into convergence problems. The constraint on the dimensionality of the problem is relieved by the introduction of an energy constraint. The method is illustrated with a complete active space valence-bond (CASVB) analysis of the charge/bond resonance electronic structure of a monomethine cyanine: Michler’s hydrol blue. The diabatic CASVB representation is shown to vary weakly for “temperatures” corresponding to visible photon energies. Canonical-ensemble SA-CASSCF enables the resolution of energies and couplings for all covalent and ionic CASVB structures contributing to the SA-CASSCF ensemble. The CASVB solution describes resonance of charge- and bond-localized electronic structures interacting via bridge resonance superexchange. The resonance couplings can be separated into channels associated with either covalent charge delocalization or chemical bonding interactions, with the latter significantly stronger than the former.« less
  • We report the first determination of a {open_quotes}most{close_quotes} diabatic basis for a triatomic molecule based exclusively on {ital ab initio} derivative couplings that takes careful account of the limitations imposed by the nonremovable part of those couplings. Baer [Chem. Phys. Lett. {bold 35}, 112 (1975)] showed that an orthogonal transformation from adiabatic states to diabatic states cannot remove all the derivative coupling unless the curl of the derivative coupling vanishes. Subsequently, Mead and Truhlar [J. Chem. Phys. {bold 77}, 6090 (1982)] observed that this curl does not, in general, vanish so that some of the derivative coupling is nonremovable. Thismore » observation and the historical lack of efficient algorithms for the evaluation of the derivative coupling led to a variety of methods for determining approximate diabatic bases that avoid computation of the derivative couplings. These methods neglect an indeterminate portion of the derivative coupling. Mead and Truhlar also observed that near an avoided crossing of two states the rotation angle to a most diabatic basis, i.e., the basis in which the removable part of the derivative coupling has been transformed away, could be obtained from the solution of a Poisson{close_quote}s equation requiring only knowledge of the derivative couplings. Here a generalization of this result to the case of a conical intersection is used to determine a most diabatic basis for a section of the 1thinsp{sup 1}A{sup {prime}} and 2thinsp{sup 1}A{sup {prime}} potential energy surfaces of HeH{sub 2} that includes the minimum energy point on the seam of conical intersection. {copyright} {ital 1998 American Institute of Physics.}« less
  • We present a general method for analyzing the character of singly excited states in terms of charge transfer (CT) and locally excited (LE) configurations. The analysis is formulated for configuration interaction singles (CIS) singly excited wave functions of aggregate systems. It also approximately works for the second-order approximate coupled cluster singles and doubles and the second-order algebraic-diagrammatic construction methods [CC2 and ADC(2)]. The analysis method not only generates a weight of each character for an excited state, but also allows to define the related quasi-diabatic states and corresponding coupling matrix elements. In the character analysis approach, we divide the targetmore » system into domains and use a modified Pipek-Mezey algorithm to localize the canonical MOs on each domain, respectively. The CIS wavefunction is then transformed into the localized basis, which allows us to partition the wavefunction into LE configurations within domains and CT configuration between pairs of different domains. Quasi-diabatic states are then obtained by mixing excited states subject to the condition of maximizing the weight of one single LE or CT configuration (localization in configuration space). Different aims of such a procedure are discussed, either the construction of pure LE and CT states for analysis purposes (by including a large number of excited states) or the construction of effective models for dynamics calculations (by including a restricted number of excited states). Applications are given to LE/CT mixing in π-stacked systems, charge-recombination matrix elements in a hetero-dimer, and excitonic couplings in multi-chromophoric systems.« less