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J V Ortiz - One of the best experts on this subject based on the ideXlab platform.
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ionization energies and dyson orbitals of the iso Electronic so2 o3 and s3 molecules from Electron Propagator calculations
Journal of Physical Chemistry A, 2021Co-Authors: Filip Pawlowski, J V OrtizAbstract:Adiabatic and vertical ionization energies corresponding to the X A12, A B22, and B A22 final states of SO2+, O3+, and S3+ have been calculated with a variety of Electron-Propagator and coupled-cluster methods. The BD-T1 Electron-Propagator method for vertical ionization energies and coupled-cluster adiabatic and zero-point corrections yield agreement with experiment to within 0.1 eV in all cases but one. The remaining discrepancies for the A B22 state of SO2+ indicate a need for higher levels of theory in determining cationic minima and their accompanying vibrational frequencies. Predictions for the still unobserved A B22 and B A22 final states of S3+ are included. To account for increased biradical character in O3 and S3, highly correlated reference states are required to produce the correct order of final states. Electron correlation plays a subtle role in determining the contours of the Dyson orbitals obtained with BD-T1 and NR2 Electron-Propagator calculations.
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Electron Propagator Methods for Vertical Electron Detachment Energies of Anions: Benchmarks and Case Studies.
Journal of chemical theory and computation, 2018Co-Authors: Manuel Díaz-tinoco, H H Corzo, J V OrtizAbstract:Ab initio Electron Propagator methods are efficient and accurate means of calculating vertical Electron detachment energies of closed-shell, molecular anions with nuclei from the first three periods. Basis set extrapolations enable definitive comparisons between Electron Propagator results and benchmarks defined by total energy differences obtained with coupled-cluster, single, double, plus perturbative triple substitution theory. The best compromises of accuracy and efficiency are provided by the renormalized, partial third-order, diagonal (P3+) self-energy and by the nondiagonal, renormalized, second-order (NR2) approximation. The outer-valence Green function, the two-particle-one-hole Tamm-Dancoff approximation, the third-order algebraic diagrammatic construction, and the renormalized third-order methods also are examined. A detailed analysis of errors for small anions is performed. Case studies include F-(H2O) and Cl-(H2O) complexes, C5H5-, two P2N3- pentagonal rings, and a superhalide, Al(BO2)4-, whose Electron detachment energy is more than double those of the halide anions. These applications illustrate the versatility of Electron Propagator methods, their utility for interpreting negative-ion photoElectron spectra, and their promise in the discovery of unusual properties and patterns of chemical bonding. Composite methods, which combine basis set effects calculated at the relatively efficient diagonal, second-order level and higher correlation effects calculated with small basis sets, provide excellent estimates of basis set-extrapolated P3+ or NR2 results and facilitate applications to large molecules. In the P3+ and NR2 methods, a judicious choice of low-order couplings between hole operators that correspond to the assumptions of Koopmans's theorem and operators that describe final-state relaxation and polarization and initial-state correlation leads to predictive accuracy, computational efficiency, and interpretive lucidity.
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mgh rydberg series transition energies from Electron Propagator theory and oscillator strengths from the molecular quantum defect orbital method
Journal of Quantitative Spectroscopy & Radiative Transfer, 2018Co-Authors: H H Corzo, A M Velasco, C Lavin, J V OrtizAbstract:Abstract Vertical excitation energies belonging to several Rydberg series of MgH have been inferred from 3+ Electron-Propagator calculations of the Electron affinities of MgH+ and are in close agreement with experiment. Many Electronically excited states with n > 3 are reported for the first time and new insight is given on the assignment of several Rydberg series. Valence and Rydberg excited states of MgH are distinguished respectively by high and low pole strengths corresponding to Dyson orbitals of Electron attachment to the cation. By applying the Molecular Quantum Defect Orbital method, oscillator strengths for Electronic transitions involving Rydberg states also have been determined.
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assessment of Electron Propagator methods for the simulation of vibrationally resolved valence and core photoionization spectra
Journal of Chemical Theory and Computation, 2017Co-Authors: Alberto Baiardi, V G Zakrzewski, Lorenzo Paoloni, Vincenzo Barone, J V OrtizAbstract:The analysis of photoElectron spectra is usually facilitated by quantum mechanical simulations. Because of the recent improvement of experimental techniques, the resolution of experimental spectra is rapidly increasing, and the inclusion of vibrational effects is usually mandatory to obtain a reliable reproduction of the spectra. With the aim of defining a robust computational protocol, a general time-independent formulation to compute different kinds of vibrationally resolved Electronic spectra has been generalized to also support photoElectron spectroscopy. The Electronic structure data underlying the simulation are computed using different Electron Propagator approaches. In addition to the more standard approaches, a new and robust implementation of the second-order self-energy approximation of the Electron Propagator based on a transition operator reference (TOEP2) is presented. To validate our implementation, a series of molecules has been used as test cases. The result of the simulations shows that,...
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interpreting bonding and spectra with correlated one Electron concepts from Electron Propagator theory
Annual Reports in Computational Chemistry, 2017Co-Authors: J V OrtizAbstract:Abstract Electron Propagator theory provides a strategy with computational and interpretive advantages for the prediction of Electron attachment and detachment energies and other properties of molecules and molecular ions. Although the effects of Electron correlation may be systematically included up to the exact limit, transparent generalizations of one-Electron concepts also are procured by the Electron Propagator approach to molecular Electronic structure. Generalized molecular-orbital concepts emerge from the Dyson quasiparticle equation, including correlated Electron binding energies and their Dyson orbitals. This information suffices to predict transition probabilities which are probed in various kinds of spectroscopic and scattering experiments. Relationships between correlated transition and reference-state properties are discussed. Approximations in the self-energy operator, wherein relaxation and correlation effects on Electron binding energies reside, are described. Emphasis is placed on approaches that employ a separation between occupied and virtual spin-orbitals such as the renormalized partial third order, the nondiagonal renormalized second order, the second-order transition operator and the Brueckner-doubles, triple-index ionization operator methods. Computational characteristics of these methods are compared with those of older precedents, including the second order, outer valence green function, and GW self-energies. Results of numerical tests on molecules of general interest and improved strategies for treating basis-set effects are reviewed. Recent and noteworthy applications to molecular wires, solvated molecules and ions, gas-phase anions, super-halogens, positron–molecule complexes, anionic resonances, and photoionization cross sections are summarized.
Danny L Yeager - One of the best experts on this subject based on the ideXlab platform.
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the complex scaled multiconfigurational spin tensor Electron Propagator method for low lying shape resonances in be mg and ca
Principles and Practice of Constraint Programming, 2017Co-Authors: Tsednee Tsogbayar, Danny L YeagerAbstract:Abstract We further apply the complex scaled multiconfigurational spin-tensor Electron Propagator method (CMCSTEP) for the theoretical determination of resonance parameters with Electron-atom systems including open-shell and highly correlated (non-dynamical correlation) atoms and molecules. The multiconfigurational spin-tensor Electron Propagator method (MCSTEP) developed and implemented by Yeager and his coworkers for real space gives very accurate and reliable ionization potentials and Electron affinities. CMCSTEP uses a complex scaled multiconfigurational self-consistent field (CMCSCF) state as an initial state along with a dilated Hamiltonian where all of the Electronic coordinates are scaled by a complex factor. CMCSTEP is designed for determining resonances. We apply CMCSTEP to get the lowest 2 P (Be − , Mg − ) and 2 D (Mg − , Ca − ) shape resonances using several different basis sets each with several complete active spaces. Many of these basis sets we employ have been used by others with different methods. Hence, we can directly compare results with different methods but using the same basis sets.
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Electron atom scattering resonances complex scaled multiconfigurational spin tensor Electron Propagator method for b shape resonances
Physical Review A, 2015Co-Authors: Tsogbayar Tsednee, Danny L YeagerAbstract:We develop the complex-scaled multiconfigurational spin-tensor Electron Propagator (CMCSTEP) technique for the theoretical determination of resonance parameters with Electron-atom--molecule systems including open-shell and highly correlated (nondynamical correlation) atoms and molecules. The multiconfigurational spin-tensor Electron Propagator method developed and implemented by Yeager and his coworkers in real space gives very accurate and reliable ionization potentials and Electron affinities. The CMCSTEP method uses a complex-scaled multiconfigurational self-consistent field state as an initial state along with a dilated Hamiltonian where all of the Electronic coordinates are scaled by a complex factor. We apply the CMCSTEP and the related ${\text{M}}_{1}$ methods to get the ${\text{B}}^{\ensuremath{-}}$ shape resonance parameters using $14s11p$ and $14s11p5d$ basis sets with $1s2s2p3s$, $1s2s2p3s3p$, $1s2s2p3d$, $2s2p3s3p$, $2s2p3d$, and $2s2p3s3p3d$ complete active spaces. The CMCSTEP and ${\text{M}}_{1}$ resonance positions and widths are obtained for the $1{s}^{2}2{s}^{2}2{p}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}D$, $1{s}^{2}2s2{p}^{3}{\phantom{\rule{0.16em}{0ex}}}^{3}D$, and $1s2{s}^{2}2{p}^{3}{\phantom{\rule{0.16em}{0ex}}}^{3}D$, ${}^{3}S$, and ${}^{3}P$ shape resonances.
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Electron atom resonances the complex scaled multiconfigurational spin tensor Electron Propagator method for the 2 p be shape resonance problem
Physical Review A, 2015Co-Authors: Tsogbayar Tsednee, Liyuan Liang, Danny L YeagerAbstract:We propose and develop the complex-scaled multiconfigurational spin-tensor Electron Propagator (CMCSTEP) technique for theoretical determination of resonance parameters with Electron-atom and Electron-molecule systems including open-shell and highly correlated atoms and molecules. The multiconfigurational spin-tensor Electron Propagator (MCSTEP) method developed and implemented by Yeager and co-workers in real space gives very accurate and reliable ionization potentials and attachment energies. The CMCSTEP method uses a complex-scaled multiconfigurational self-consistent field (CMCSCF) state as an initial state along with a dilated Hamiltonian where all of the Electronic coordinates are scaled by a complex factor. The CMCSCF was developed and applied successfully to resonance problems earlier. We apply the CMCSTEP method to get ${}^{2}P\phantom{\rule{0.16em}{0ex}}{\text{Be}}^{\ensuremath{-}}$ shape resonance parameters using $14s11p5d,\phantom{\rule{0.16em}{0ex}}14s14p2d$, and $14s14p5d$ basis sets with a $2s2p3d$ complete active space. The obtained values of the resonance parameters are compared to previous results. Here CMCSTEP has been developed and used for a resonance problem. It appears to be among the most accurate and reliable techniques. Vertical ionization potentials and attachment energies in real space are typically within $\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.28em}{0ex}}\text{eV}$ or better of excellent experimental results and full configuration-interaction calculations with a good basis set. We expect the same sort of agreement in complex space.
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equivalent orbitals for multiconfigurational spin tensor Electron Propagator method mcstep the vertical ionization potentials of b no cf and of
International Journal of Quantum Chemistry, 2008Co-Authors: Danny L YeagerAbstract:The multiconfigurational spin tensor Electron Propagator method (MCSTEP) was developed as an implementation of Electron Propagator/single particle Green's function methods for ionization potentials (IPs) and Electron affinities (EAs). MCSTEP was specifically designed for open shell and highly correlated (nondynamically correlated) initial states. For computational efficiency the initial state used in MCSTEP is typically a small complete active space (CAS) multiconfigurational self-consistent field (MCSCF) state. If in a molecule there are some degenerate orbitals which are not fully or half occupied, usual MCSCF calculations will make these orbitals inequivalent, i.e., the occupied ones will be different from the nonoccupied ones, so that the degeneracy is broken. In this article, we use a state averaged MCSCF method to get equivalent orbitals for the initial state and import the integrals into the subsequent MCSTEP calculations. This gives, in general, more reliable MCSTEP vertical IPs. © 2008 Wiley Periodicals, Inc., 2008
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Approximate MCSCF optimization for multiconfigurational spin-tensor Electron Propagator method (MCSTEP): The vertical ionization potentials of CO, HCN, HNC, H2CO, and O3
International Journal of Quantum Chemistry, 2007Co-Authors: Danny L YeagerAbstract:The multiconfigurational spin tensor Electron Propagator method (MCSTEP) was developed as an implementation of Electron Propagator/single particle Green's function methods. MCSTEP was specifically designed for open shell and highly correlated (nondynamically correlated) initial states. The initial state used in MCSTEP is typically a small complete active space (CAS) with multiconfigurational self-consistent field (MCSCF) state. In some cases, because of our use of a small CAS in MCSTEP, the Lagrangian eigenvalues of the MCSCF reference state are in an undesired order (u). The desired order (d) can usually be obtained by excluding one or more orbital rotations in MCSCF optimization between the doubly occupied and partially occupied orbitals. We systematically examine several cases where the undesired order occurs for the low-lying vertical MCSTEP ionization potentials (IPs) of the molecules CO, HCN, HNC, H2CO, and O3 with our recently established CAS choices for MCSCF/MCSTEP. By excluding one or more orbital rotations between the partially and doubly occupied orbitals, an approximate MCSCF reference state with the same CAS choice is obtained for use in standard MCSTEP calculations that, in general, gives more reliable vertical MCSTEP IPs. © 2007 Wiley Periodicals, Inc. J Quantum Chem, 2008
V G Zakrzewski - One of the best experts on this subject based on the ideXlab platform.
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assessment of Electron Propagator methods for the simulation of vibrationally resolved valence and core photoionization spectra
Journal of Chemical Theory and Computation, 2017Co-Authors: Alberto Baiardi, V G Zakrzewski, Lorenzo Paoloni, Vincenzo Barone, J V OrtizAbstract:The analysis of photoElectron spectra is usually facilitated by quantum mechanical simulations. Because of the recent improvement of experimental techniques, the resolution of experimental spectra is rapidly increasing, and the inclusion of vibrational effects is usually mandatory to obtain a reliable reproduction of the spectra. With the aim of defining a robust computational protocol, a general time-independent formulation to compute different kinds of vibrationally resolved Electronic spectra has been generalized to also support photoElectron spectroscopy. The Electronic structure data underlying the simulation are computed using different Electron Propagator approaches. In addition to the more standard approaches, a new and robust implementation of the second-order self-energy approximation of the Electron Propagator based on a transition operator reference (TOEP2) is presented. To validate our implementation, a series of molecules has been used as test cases. The result of the simulations shows that,...
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composite Electron Propagator methods for calculating ionization energies
Journal of Chemical Physics, 2016Co-Authors: Manuel Diaztinoco, O Dolgounitcheva, V G Zakrzewski, J V OrtizAbstract:Accurate ionization energies of molecules may be determined efficiently with composite Electron-Propagator (CEP) techniques. These methods estimate the results of a calculation with an advanced correlation method and a large basis set by performing a series of more tractable calculations in which large basis sets are used with simpler approximations and small basis sets are paired with more demanding correlation techniques. The performance of several CEP methods, in which diagonal, second-order Electron Propagator results with large basis sets are combined with higher-order results obtained with smaller basis sets, has been tested for the ionization energies of closed-shell molecules from the G2 set. Useful compromises of accuracy and computational efficiency employ complete-basis-set extrapolation for second-order results and small basis sets in third-order, partial third-order, renormalized partial-third order, or outer valence Green’s function calculations. Analysis of results for vertical as well as adiabatic ionization energies leads to specific recommendations on the best use of regular and composite methods. Results for 22 organic molecules of interest in the design of photovoltaic devices, benzo[a]pyrene, Mg-octaethylporphyrin, and C60 illustrate the capabilities of CEP methods for calculations on large molecules.
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accurate ionization potentials and Electron affinities of acceptor molecules iv Electron Propagator methods
Journal of Chemical Theory and Computation, 2016Co-Authors: O Dolgounitcheva, Manuel Diaztinoco, V G Zakrzewski, Ryan M Richard, Noa Marom, David C Sherrill, J V OrtizAbstract:Comparison of ab initio Electron-Propagator predictions of vertical ionization potentials and Electron affinities of organic, acceptor molecules with benchmark calculations based on the basis set-extrapolated, coupled cluster single, double, and perturbative triple substitution method has enabled identification of self-energy approximations with mean, unsigned errors between 0.1 and 0.2 eV. Among the self-energy approximations that neglect off-diagonal elements in the canonical, Hartree–Fock orbital basis, the P3 method for Electron affinities, and the P3+ method for ionization potentials provide the best combination of accuracy and computational efficiency. For approximations that consider the full self-energy matrix, the NR2 methods offer the best performance. The P3+ and NR2 methods successfully identify the correct symmetry label of the lowest cationic state in two cases, naphthalenedione and benzoquinone, where some other methods fail.
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nr2 and p3 accurate efficient Electron Propagator methods for calculating valence vertical ionization energies of closed shell molecules
Journal of Physical Chemistry A, 2015Co-Authors: H H Corzo, V G Zakrzewski, O Dolgounitcheva, Annia Galano, J V OrtizAbstract:Two accurate and computationally efficient Electron-Propagator (EP) methods for calculating the valence, vertical ionization energies (VIEs) of closed–shell molecules have been identified through comparisons with related approximations. VIEs of a representative set of closed-shell molecules were calculated with EP methods using 10 basis sets. The most easily executed method, the diagonal, second-order (D2) EP approximation, produces results that steadily rise as basis sets are improved toward values based on extrapolated coupled-cluster singles and doubles plus perturbative triples calculations, but its mean errors remain unacceptably large. The outer valence Green function, partial third-order and renormalized partial third-order methods (P3+), which employ the diagonal self-energy approximation, produce markedly better results but have a greater tendency to overestimate VIEs with larger basis sets. The best combination of accuracy and efficiency with a diagonal self-energy matrix is the P3+ approximatio...
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Electron Propagator calculations on the ground and excited states of c60
Journal of Physical Chemistry A, 2014Co-Authors: V G Zakrzewski, O Dolgounitcheva, J V OrtizAbstract:Electron Propagator calculations in two approximations—the third-order algebraic, diagrammatic construction and the outer valence Green’s function (OVGF)—have been performed on the vertical Electron affinities of C60 and the vertical Electron detachment energies of several states of C60– with a variety of basis sets. These calculations predict bound 2T1u and 2T1g anions, but fail to produce 2T2u or 2Hg anionic states that are more stable than ground-state C60. The Electron affinity for the 2Ag state is close to zero, but no definitive result on its sign has been obtained. This state may be a resonance or marginally bound anion. The OVGF prediction for the vertical Electron detachment energy of 2T1u C60–, 2.63 eV, is in excellent agreement with recent anion photoElectron spectra.
Joseph T. Golab - One of the best experts on this subject based on the ideXlab platform.
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Comparison of perturbative and multiconfigurational Electron Propagator methods
International Journal of Quantum Chemistry, 1996Co-Authors: V G Zakrzewski, Danny L Yeager, J V Ortiz, Jeffrey A. Nichols, Dodi Heryadi, Joseph T. GolabAbstract:Ionization energies below 20 eV of 10 molecules calculated with Electron Propagator techniques employing Hartree-Fock orbitals and multiconfigurational self-consistent field orbitals are compared. Diagonal and nondiagonal self-energy approximations are used in the perturbative formalism. Three diagonal methods based on second- and third-order self-energy terms, all known as the outer valence Green's function, are discussed. A procedure for selecting the most reliable of these three versions for a given calculation is tested. Results with a polarized, triple ζ basis produce root mean square errors with respect to experiment of approximately 0.3 eV. Use of the selection procedure has a slight influence on the quality of the results. A related, nondiagonal method, known as ADC(3), performs infinite-order summations on several types of self-energy contributions, is complete through third-order, and produces similar accuracy. These results are compared to ionization energies calculated with the multiconfigurational spin-tensor Electron Propagator method. Complete active space wave functions or close approximations constitute the reference states. Simple field operators and transfer operators pertaining to the active space define the operator manifold. With the same basis sets, these methods produce ionization energies with accuracy that is comparable to that of the perturbative techniques. © 1996 John Wiley & Sons, Inc.
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The multiconfigurational spin tensor Electron Propagator method (MCSTEP): Comparison with extended Koopmans' theorem results
Theoretica chimica acta, 1995Co-Authors: Dodi Heryadi, Danny L Yeager, Joseph T. Golab, Jeffrey A. NicholsAbstract:We applied the multiconfigurational spin tensor Electron Propagator method (MCSTEP) for determining the lowest few (in energy) vertical ionization potentials (IPs) of HF, H_2O, NH_3, CH_4, N_2, CO, HNC, HCN, C_2H_2, H_2CO, and B_2H_6. We chose these molecules so that we could compare MCSTEP IPs with recently reported extended Koopmans' theorem (EKT) IPs on the same molecules. Using standard Dunning core-valence basis sets with relatively small complete active spaces, MCSTEP results are in very good to excellent agreement with experiment. These MCSTEP IPs are obtained using matrices no larger than 400 × 400. EKT matrices are even smaller; however, to obtain similar but generally slightly worse agreement with experiment, fairly large active spaces are required with EKT.
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the potential energy curves of the x 2πg a 4πu a 2πu b 4σ g b 2σ g 2πu and c 4σ u states of o 2 obtained using the multiconfigurational spin tensor Electron Propagator method
Journal of Chemical Physics, 1994Co-Authors: Danny L Yeager, Jeffrey A. Nichols, Joseph T. GolabAbstract:With Electron Propagator methods, Electronic ionization and attachment energies are obtained directly. The multiconfigurational spin tensor Electron Propagator method (MCSTEP) is explicitly designed for systems with open shell and/or nondynamical correlation in the initial state. We apply MCSTEP to O2 at several internuclear separations and obtain and report the MCSTEP potential energy curves and the spectroscopic constants for the X 2Πg, a 4Πu, A 2Πu, b 4Σ−g, B 2Σ−g, 2Πu, and c 4Σ−u states of O+2.
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ionization potentials of ch2 a comparison of the multiconfigurational spin tensor Electron Propagator method with benchmark full configuration interaction and large scale multireference configuration interaction calculations
Journal of Chemical Physics, 1994Co-Authors: Jeffrey A. Nichols, Danny L Yeager, Dodi Heryadi, Joseph T. GolabAbstract:Using the same basis sets and geometries as were previously used in ‘‘benchmark’’ full configuration interaction (FCI) calculations we compare the multiconfigurational spin tensor Electron Propagator method (MCSTEP) with FCI for the vertical ionization potentials (IPs) in CH2 below 19.0 eV. Our results show that MCSTEP using a full valence complete active space MCSCF initial state accurately obtains the lowest several principal vertical ionization potentials. We also determine vertical and adiabatic IPs in CH2 with MCSTEP using larger bases and compare to accurate large scale multireference singles and doubles CI with quadruple excitations estimated via a Davidson correction.
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Multiconfigurational spin tensor Electron Propagator Electron affinities for F, BO, CN, OH, and NH2
The Journal of Chemical Physics, 1992Co-Authors: Danny L Yeager, Jeffrey A. Nichols, Joseph T. GolabAbstract:We applied the multiconfigurational spin tensor Electron Propagator method (MCSTEP) to the systems F, OH, NH2, BO, and CN for the determination of vertical and adiabatic Electron affinities (EAs). These are the first MCSTEP EA calculations for systems that are not pseudo two‐Electron systems and the first time MCSTEP is used for EAs of molecules. Using standard Dunning core‐valence basis sets supplemented with diffuse functions and with relatively small complete active spaces, MCSTEP results are in very good to excellent agreement with experiment. Comparisons with EAs determined by other methods using exactly the same basis sets show that MCSTEP is generally more consistent and reliable.
O Dolgounitcheva - One of the best experts on this subject based on the ideXlab platform.
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composite Electron Propagator methods for calculating ionization energies
Journal of Chemical Physics, 2016Co-Authors: Manuel Diaztinoco, O Dolgounitcheva, V G Zakrzewski, J V OrtizAbstract:Accurate ionization energies of molecules may be determined efficiently with composite Electron-Propagator (CEP) techniques. These methods estimate the results of a calculation with an advanced correlation method and a large basis set by performing a series of more tractable calculations in which large basis sets are used with simpler approximations and small basis sets are paired with more demanding correlation techniques. The performance of several CEP methods, in which diagonal, second-order Electron Propagator results with large basis sets are combined with higher-order results obtained with smaller basis sets, has been tested for the ionization energies of closed-shell molecules from the G2 set. Useful compromises of accuracy and computational efficiency employ complete-basis-set extrapolation for second-order results and small basis sets in third-order, partial third-order, renormalized partial-third order, or outer valence Green’s function calculations. Analysis of results for vertical as well as adiabatic ionization energies leads to specific recommendations on the best use of regular and composite methods. Results for 22 organic molecules of interest in the design of photovoltaic devices, benzo[a]pyrene, Mg-octaethylporphyrin, and C60 illustrate the capabilities of CEP methods for calculations on large molecules.
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accurate ionization potentials and Electron affinities of acceptor molecules iv Electron Propagator methods
Journal of Chemical Theory and Computation, 2016Co-Authors: O Dolgounitcheva, Manuel Diaztinoco, V G Zakrzewski, Ryan M Richard, Noa Marom, David C Sherrill, J V OrtizAbstract:Comparison of ab initio Electron-Propagator predictions of vertical ionization potentials and Electron affinities of organic, acceptor molecules with benchmark calculations based on the basis set-extrapolated, coupled cluster single, double, and perturbative triple substitution method has enabled identification of self-energy approximations with mean, unsigned errors between 0.1 and 0.2 eV. Among the self-energy approximations that neglect off-diagonal elements in the canonical, Hartree–Fock orbital basis, the P3 method for Electron affinities, and the P3+ method for ionization potentials provide the best combination of accuracy and computational efficiency. For approximations that consider the full self-energy matrix, the NR2 methods offer the best performance. The P3+ and NR2 methods successfully identify the correct symmetry label of the lowest cationic state in two cases, naphthalenedione and benzoquinone, where some other methods fail.
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Electron detachment energies of aqueous and cluster halide anions from Electron Propagator calculations with the polarizable continuum model
International Journal of Quantum Chemistry, 2012Co-Authors: O Dolgounitcheva, V G Zakrzewski, J V OrtizAbstract:To calibrate computational studies of photoElectron spectra of dissolved anions, the vertical Electron detachment energies (VEDEs) of the fluoride and chloride anions in isolation and in the presence of six coordinated water molecules have been calculated with and without the polarizable continuum model (PCM) of solvation in water. Large shifts in VEDEs and important changes in coordination geometries about the chloride anion occur with the use of the PCM. Cluster and PCM calculations confirm previous, qualitative conclusions on Dyson orbitals corresponding to the lowest VEDEs of aqueous halide anions. For the fluoride case, Dyson orbitals for the lowest VEDEs are spread over water molecules, not the anion, but for the chloride case, the Dyson orbitals for the lowest VEDEs are localized on the anion. The partial third-order (P3) and P3+ approximations of Electron Propagator theory provide a reliable means to calculating VEDEs with polarized atomic basis sets. © 2012 Wiley Periodicals, Inc.
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Electron Propagator and coupled cluster calculations on the photoElectron spectra of thiouracil and dithiouracil anions
Journal of Chemical Physics, 2011Co-Authors: O Dolgounitcheva, V G Zakrzewski, J V OrtizAbstract:Electron affinities, vertical Electron detachment energies, and isomerization energies of 4-thiouracil, 2-thiouracil, and 2,4-dithiouracil and their valence anions have been calculated with ab initio Electron Propagator and other many-body methods. Anions in which protons have been transferred to the C5 from the N1 or N3 ring positions have been considered, but the canonical forms are most stable for the 4-thiouracil and 2,4-dithiouracil anions. Electron affinities of 0.61, 0.26, and 0.87 eV have been determined for 4-thiouracil, 2-thiouracil, and 2,4-dithiouracil, respectively. Electron Propagator calculations on the canonical anions yield vertical Electron detachment energies that are in close agreement with experimental peaks at 1.05, 3.21, and 3.32 eV for 4-thiouracil and at 1.4 eV for 2,4-dithiouracil.
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Ab initio Electron Propagator methods: Applications to nucleic acids fragments and metallophthalocyanines
International Journal of Quantum Chemistry, 2010Co-Authors: V G Zakrzewski, O Dolgounitcheva, Alexander V. Zakjevskii, J V OrtizAbstract:Electron Propagator methods provide accurate and efficient determinations of Electron binding energies and retain many interpretive advantages through their generation of associated Dyson orbitals. Methods that are based on the diagonal self-energy approximation have been applied to nucleic acid fragments such as nucleotides and dinucleotides. These calculations can be made more feasible for larger systems through the introduction of quasiparticle virtual orbitals. Nondiagonal, renormalized self-energies are needed for systems where correlation final states with low-pole strengths are present. Applications to zinc phthalocyanine illustrate such capabilities. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010