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Garrett NR, Davis MC, Fortenberry RC. DFT + F12 QFFs for Cost-Effective Rovibrational Spectral Data Predictions of Ground and Excited Electronic States. J Chem Theory Comput 2024. [PMID: 38230913 DOI: 10.1021/acs.jctc.3c01179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
The quest for faster computation of anharmonic vibrational frequencies of both ground and excited electronic states has led to combining coupled cluster theory harmonic force constants with density functional theory cubic and quartic force constants for defining a quartic force field (QFF) utilized in conjunction with vibrational perturbation theory at second order (VPT2). This work shows that explicitly correlated coupled cluster theory at the singles, doubles, and perturbative triples levels [CCSD(T)-F12] provides accurate anharmonic vibrational frequencies and rotational constants when conjoined with any of B3LYP, CAM-B3LYP, BHandHLYP, PBE0, and ωB97XD for roughly one-quarter of the computational time of the CCSD(T)-F12 QFF alone for our test set. As the number of atoms in the molecule increases, however, the anharmonic terms become a greater portion of the QFF, and the cost comparison improves with HOCO+ and formic acid, requiring less than 15 and 10% of the time, respectively. In electronically excited states, PBE0 produces more consistently accurate results. Additionally, as the size of the molecule and, in turn, QFF increase, the cost savings for utilizing such a hybrid approach for both ground- and excited-state computations grows. As such, these methods are promising for predicting accurate rovibrational spectral properties for electronically excited states. In cases where well-behaved potentials for a small selection of targeted excited states are needed, such an approach should reduce the computational cost compared to that of methods requiring semiglobal potential surfaces or variational treatments of the rovibronic Hamiltonian. Such applications include spectral characterization of comets, exoplanets, or any situation in which gas phase molecules are being excited by UV-vis radiation.
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Affiliation(s)
- Noah R Garrett
- Department of Chemistry & Biochemistry, University of Mississippi, University, Mississippi 38677-1848, United States
| | - Megan C Davis
- Theoretical Division, T-1, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ryan C Fortenberry
- Department of Chemistry & Biochemistry, University of Mississippi, University, Mississippi 38677-1848, United States
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Mosley JD, Cheng TC, McCoy AB, Duncan MA. Infrared Spectroscopy of the Mass 31 Cation: Protonated Formaldehyde vs Methoxy. J Phys Chem A 2012; 116:9287-94. [DOI: 10.1021/jp3072298] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J. D. Mosley
- Department of Chemistry, University of Georgia, Athens, Georgia
30602, United States
| | - T. C. Cheng
- Department of Chemistry, University of Georgia, Athens, Georgia
30602, United States
| | - A. B. McCoy
- Department of Chemistry, The Ohio State University, Columbus,
Ohio 43210, United States
| | - M. A. Duncan
- Department of Chemistry, University of Georgia, Athens, Georgia
30602, United States
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Reimers JR, Cai ZL. Hydrogen bonding and reactivity of water to azines in their S1 (n,π*) electronic excited states in the gas phase and in solution. Phys Chem Chem Phys 2012; 14:8791-802. [DOI: 10.1039/c2cp24040h] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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4
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Yabuno Y, Hiraga Y, Takagi R, Abe M. Concentration and Temperature Dependency of Regio- and Stereoselectivity in a Photochemical [2 + 2] Cycloaddition Reaction (the Paternò−Büchi Reaction): Origin of the Hydroxy-Group Directivity. J Am Chem Soc 2011; 133:2592-604. [DOI: 10.1021/ja1088524] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Youhei Yabuno
- Department of Chemistry, Graduate School of Science, Hiroshima University (HIRODAI), 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and
| | - Yoshikazu Hiraga
- Department of Chemistry, Graduate School of Science, Hiroshima University (HIRODAI), 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and
| | - Ryukichi Takagi
- Department of Chemistry, Graduate School of Science, Hiroshima University (HIRODAI), 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and
| | - Manabu Abe
- Department of Chemistry, Graduate School of Science, Hiroshima University (HIRODAI), 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and
- Japan Science and Technology Agency, CREST, 5 Sanbancho, Chiyodaku, Tokyo, 102-0075, Japan
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PITARCH-RUIZ JOSE, SANCHEZ-MARIN JOSE, DE MERAS ALFREDOSANCHEZ, MAYNAU DANIEL. The vertical spectrum of H2CO revisited: (SC)2-CI and CC calculations. Mol Phys 2009. [DOI: 10.1080/0026897021000034503] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- JOSE PITARCH-RUIZ
- a Departament de Quimica-Fisica , Institut de Ciencia Molecular, Facultat de Ciencies Quimiques, Universitat de Valencia , Dr. Moliner 50, E-46100 , Burjassot (Valencia) , Spain
| | - JOSE SANCHEZ-MARIN
- a Departament de Quimica-Fisica , Institut de Ciencia Molecular, Facultat de Ciencies Quimiques, Universitat de Valencia , Dr. Moliner 50, E-46100 , Burjassot (Valencia) , Spain
| | - ALFREDO SANCHEZ DE MERAS
- a Departament de Quimica-Fisica , Institut de Ciencia Molecular, Facultat de Ciencies Quimiques, Universitat de Valencia , Dr. Moliner 50, E-46100 , Burjassot (Valencia) , Spain
| | - DANIEL MAYNAU
- b Laboratoire de Physique Quantique, URA 505 , Université Paul Sabatier , 118 route de Narbonne, 31062 , Toulouse Cedex , France
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Zhang P, Maeda S, Morokuma K, Braams BJ. Photochemical reactions of the low-lying excited states of formaldehyde: T1/S0 intersystem crossings, characteristics of the S1 and T1 potential energy surfaces, and a global T1 potential energy surface. J Chem Phys 2009; 130:114304. [DOI: 10.1063/1.3085952] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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7
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Castro ME, Niño A, Muñoz-Caro C. Structural and vibrational theoretical analysis of protonated formaldehyde in its $$\tilde{X}^{1} A^{\prime}$$ ground electronic state. Theor Chem Acc 2007. [DOI: 10.1007/s00214-007-0392-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Karpfen A, Kryachko ES. Blue-Shifted A−H Stretching Modes and Cooperative Hydrogen Bonding. 1. Complexes of Substituted Formaldehyde with Cyclic Hydrogen Fluoride and Water Clusters. J Phys Chem A 2007; 111:8177-87. [PMID: 17661452 DOI: 10.1021/jp072717f] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structures and vibrational spectra of the intermolecular complexes formed by insertion of substituted formaldehyde molecules HRCO (R = H, Li, F, Cl) into cyclic hydrogen fluoride and water clusters are studied at the MP2/aug-cc-pVTZ computational level. Depending on the nature of the substituent R, the cluster type, and its size, the C-H stretching modes of HRCO undergo large blue and partly red shifts, whereas all the F-H and O-H stretching modes of the conventional hydrogen bonds are strongly red-shifted. It is shown that (i) the mechanism of blue shifting can be explained within the concept of the negative intramolecular coupling between C-H and C=O bonds that is inherent to the HRCO monomers, (ii) the blue shifts also occur even if no hydrogen bond is formed, and (iii) variation of the acceptor X or the strength of the C-H...X hydrogen bond may either amplify the blue shift or cause a transition from blue shift to red shift. These findings are illustrated by means of intra- and intermolecular scans of the potential energy surfaces. The performance of the negative intramolecular coupling between C-H and C=O bonds of H(2)CO is interpreted in terms of the NBO analysis of the isolated H(2)CO molecule and H(2)CO interacting with (H2O)n and (HF)n clusters.
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Affiliation(s)
- Alfred Karpfen
- Institute for Theoretical Chemistry, University of Vienna, Währinger Strasse 17, A-1090 Vienna, Austria.
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Abstract
The title unknown reaction is theoretically studied at various levels to probe the interaction mechanism between the ethynyl radical (HC triple bond C) and formaldehyde (H(2)C double bond O). The most feasible pathway is a barrier-free direct H-abstraction process leading to acetylene and formyl radical (C(2)H(2)+HCO) via a weakly bound complex, and then the product can take secondary dissociation to the final product C(2)H(2)+CO+H. The C-addition channel leading to propynal plus H-atom (HCCCHO+H) has the barrier of only 3.6, 2.9, and 2.1 kcal/mol at the CCSD(T)/6-311+G(3df,2p)MP2//6-311G(d,p)+ZPVE, CCSD(T)/6-311+G(3df,2p)//QCISD/6-311G(d,p)+ZPVE, and G3//MP2 levels, respectively [CCSD(T)--coupled cluster with single, double, and triple excitations; ZPVE--zero-point vibrational energy; QCISD--quadratic configuration interaction with single and double excitations; G3//MP2-Gaussian-3 based on Moller-Plesset geometry]. The O addition also leading to propynal plus H atom needs to overcome a higher barrier of 5.3, 8.7, and 3.0 kcalmol at the three corresponding levels. The title no-barrier reaction presents a new efficient route to remove the pollutant H(2)CO, and should be included in the combustion models of hydrocarbons. It may also represent the fastest radical-H(2)CO reaction among the available theoretical data. Moreover, it could play an important role in the interstellar chemistry where the zero- or minute-barrier reactions are generally favored. Discussions are also made on the possible formation of the intriguing propynal in space via the title reaction on ice surface.
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Affiliation(s)
- Hao Dong
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
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Cai ZL, Reimers JR. The Lowest Singlet (n,π*) and (π,π*) Excited States of the Hydrogen-Bonded Complex between Water and Pyrazine. J Phys Chem A 2007; 111:954-62. [PMID: 17266237 DOI: 10.1021/jp0658142] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The hydrogen bonding between water and pyrazine in its ground, lowest (n,pi*), and lowest (pi,pi*) states is investigated using density-functional theory (DFT), time-dependent density function theory (TD-DFT), coupled-cluster singles and doubles (CCSD) theory and equation-of-motion coupled cluster (EOM-CCSD) theory. For all states, the minimum-energy configuration is found to be an orthodox linear hydrogen-bonded species, with the bond strength increasing by 0.4 kcal mol-1 upon formation of the (pi,pi*) state and decreasing by 1.0 kcal mol-1 upon formation of the (n,pi*) state. The calculated solvent shifts for the complexes match experimental data and provide a basis for the understanding of the aqueous solvation of pyrazine, and the excited-state complexes are predicted to be only short-lived, explaining the failure of molecular beam experiments to observe them. Quite a different scenario for hydrogen bonding to the (n,pi*) excited state is found compared to those of H2O:pyridine and H2O:pyrimidine: for pyridine linear hydrogen bonds are unstable and hydrogen bonds to the electron-enriched pi cloud are strong, whereas for pyrimidine the excitation localizes on the nonbonded nitrogen leaving the hydrogen-bonding unaffected. For H2O:pyrazine, the (n,pi*) excitation remains largely delocalized, providing a distinct intermediary scenario.
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Affiliation(s)
- Zheng-Li Cai
- School of Chemistry, The University of Sydney, NSW 2006, Australia
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11
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Karpfen A, Kryachko ES. Strongly Blue-Shifted C−H Stretches: Interaction of Formaldehyde with Hydrogen Fluoride Clusters. J Phys Chem A 2005; 109:8930-7. [PMID: 16834297 DOI: 10.1021/jp050408o] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The equilibrium structures, binding energies, and vibrational spectra of the cyclic, hydrogen-bonded complexes formed between formaldehyde, H(2)CO, and hydrogen fluoride clusters, (HF)(1< or =n < or =4), are investigated by means of large-scale second-order Møller-Plesset calculations with extended basis sets. All studied complexes exhibit marked blue shifts of the C-H stretching frequencies, exceeding 100 cm(-1) for n = 2-4. It is shown that these blue shifts are, however, only to a minor part caused by blue-shifting hydrogen bonding via C-H...F contacts. The major part arises due to the structural relaxation of the H(2)CO molecule under the formation of a strong C=O...H-F hydrogen bond which strengthens as n increases. The close correlation between the different structural parameters in the studied series of complexes is demonstrated, and the consequences for the frequency shifts in the complexes are pointed out, corroborating thus the suggestion of the primary role of the C=O...H-F hydrogen bonding for the C-H stretching frequency shifts. This particular behavior, that the appearance of an increasingly stronger blue shift of the C-H stretching frequencies is mainly induced by the formation of a progressively stronger C=O...H-F hydrogen bond in the series of H(2)CO...(HF)(1< or =n < or =4), complexes and only to a lesser degree by the formation of the so-called blue-shifting C-H...F hydrogen bond, is rationalized with the aid of selected sections of the intramolecular H(2)CO potential energy surface and by performing a variety of structural optimizations of the H(2)CO molecule embedded in external, differently oriented dipole electric fields, and also by invoking a simple analytical force-field model.
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Affiliation(s)
- Alfred Karpfen
- Institute for Theoretical Chemistry, University of Vienna, Währinger Strasse 17, A-1090 Vienna, Austria.
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12
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Angeli C, Borini S, Ferrighi L, Cimiraglia R. A CASSCF theoretical study of the vibrational frequencies and structure of formaldehyde, acetaldehyde and acetone valence excited states. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.theochem.2004.12.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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13
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Cai ZL, Reimers JR. First Singlet (n,π*) Excited State of Hydrogen-Bonded Complexes between Water and Pyrimidine. J Phys Chem A 2005; 109:1576-86. [PMID: 16833480 DOI: 10.1021/jp048309i] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydrogen bonds from water to excited-state formaldehyde and from water to excited-state pyridine have been shown to display novel motifs to traditional hydrogen bonds involving ground states, with, in particular for H2O:pyridine, strong interactions involving the electron-rich pi cloud dominating the (n,pi) excited state. We investigate H2O:pyrimidine and various dihydrated species and reveal another motif, one in which the hydrogen bonding can dramatically alter the electronic structure of the excited state. Such effects are rare for ground-state interactions for which hydrogen bonding usually acts to merely perturb the electronic structure of the participating molecules. It arises as the (n,pi*) excitation of isolated pyrimidine is delocalized over both nitrogens but asymmetric hydrogen bonding causes it to localize on just the noninteracting atom. As a result, the excited-state hydrogen bond in H2O:pyrimidine is suprisingly very similar to the ground-state structure. These results lead to an improved understanding of the spectroscopy of pyrimidine in liquid water, and to the prediction that stable excited-state hydrogen bonds in H2O:pyrimidine should be observable, despite failure of experiments to actually do so. They also provide a simple model for the intricate control over primary charge separation in photosynthesis exerted by hydrogen bonding, and for solvent-induced electron localization in symmetric mixed-valence complexes. All conclusions are based on strong parallels found between the results of calculations performed using density-functional theory (DFT) and time-dependent DFT (TDDFT), complete-active-space self-consistent-field (CASSCF) with second-order perturbation-theory correction (CASPT2) theory, and equation-of-motion coupled cluster (EOM-CCSD) theory, calculations that are verified through detailed comparison of computed properties with experimental data for both the isolated molecules and the ground-state hydrogen bond.
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Affiliation(s)
- Zheng-Li Cai
- School of Chemistry, The University of Sydney, NSW 2006, Australia
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14
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Wiberg KB, Wang YG, de Oliveira AE, Perera SA, Vaccaro PH. Comparison of CIS- and EOM-CCSD-Calculated Adiabatic Excited-State Structures. Changes in Charge Density on Going to Adiabatic Excited States. J Phys Chem A 2004; 109:466-77. [PMID: 16833367 DOI: 10.1021/jp040558j] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The CIS and EOM-CCSD adiabatic geometries for the first excited states of a set of small molecules (C2H4, C2H2, H2C=O, H2C=S, CS2, CO2, SO2, NO2) have been calculated using the 6-311++G** basis set to see if the former geometries can be good starting points for optimizations at the latter theoretical level. With most of the molecules, there is fairly good agreement between the results from the two methods, and EOM-CCSD gives good agreement with the available experimental data. A detailed discussion of the lowest-lying singlet excited states in CO2 and CS2 is presented, highlighting the pronounced differences in electronic character and equilibrium structure displayed by these isovalent species. The origins of the structural distortions that are frequently found for the adiabatic excited states are examined with the aid of deformation density plots and the electron localization function (ELF).
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Affiliation(s)
- Kenneth B Wiberg
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA
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Wesolowski TA. Hydrogen-Bonding-Induced Shifts of the Excitation Energies in Nucleic Acid Bases: An Interplay between Electrostatic and Electron Density Overlap Effects. J Am Chem Soc 2004; 126:11444-5. [PMID: 15366883 DOI: 10.1021/ja048846g] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The theoretically calculated dimerization-induced shifts of the lowest excitation energies in two model systems, adenine-thymine and guanine-cytosine base pairs, are analyzed. The applied formalism is based on first principles and allows one to study the influence of the microscopic environment of a given molecule on its ground- [Wesolowski, T. A.; Warshel, A. J. Phys. Chem. 1993, 97, 8050] and excited-state [Casida, M. E.; Wesolowski, T. A. Int. J. Quantum Chem. 2004, 96, 577] properties. The assessment of the relative importance of such effects as (a) Coulomb interactions, (b) orbital interactions, (c) electronic polarization of the environment, and (d) electron density overlap effects is straightforward in this formalism. In the applied formalism, electron density overlap effects can be further decomposed into the exchange-correlation component which provides a small attractive contribution and the repulsive kinetic energy-dependent component. It is shown that the shifts can be attributed to the electrostatic interactions and the repulsive overlap-dependent term in the embedding potential. The electronic polarization of the environment plays a significant role (up to 30% of the total shift) only in transitions involving the orbitals localized on hydrogen bond donor groups. For all analyzed shifts, the contribution of the intermolecular orbital interactions is negligible. The analysis of this work provides strong evidence supporting the use of the widely applied embedding-molecule strategy in computational studies of chromophores in a condensed phase even in such cases where only one end of the hydrogen bond is included in the quantum mechanical part.
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Affiliation(s)
- Tomasz A Wesolowski
- Department of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
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Abstract
The equation-of-motion coupled-cluster (EOM-CC) methods truncated after double, triple, or quadruple cluster and linear excitation operators (EOM-CCSD, EOM-CCSDT, and EOM-CCSDTQ) have been derived and implemented into parallel execution programs. They compute excitation energies, excited-state dipole moments, and transition moments of closed- and open-shell systems, taking advantage of spin, spatial (real Abelian), and permutation symmetries simultaneously and fully (within the spin-orbital formalisms). The related Lambda equation solvers for coupled-cluster (CC) methods through and up to connected quadruple excitation (CCSD, CCSDT, and CCSDTQ) have also been developed. These developments have been achieved, by virtue of the algebraic and symbolic manipulation program that automated the formula derivation and implementation altogether. The EOM-CC methods and CC Lambda equations introduce a class of second quantized ansatz with a de-excitation operator (Y), a number of excitation operators (X), and a physical (e.g., the Hamiltonian) operator (A), leading to the tensor contraction expressions that can be performed in the order of ((...((yx)x)...)x)a or ((...((ax)x)...)x)y at the minimal peak operation cost, where x, y, and a are basis-set representations (i.e., tensors) of the respective operators X, Y, and A. Any intermediate tensor resulting from either contraction order is shown to have at most six groups of permutable indices, and this knowledge is used to guide the computer-synthesized programs to fully exploit the permutation symmetry of any tensor to minimize the arithmetic and memory costs.
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Affiliation(s)
- So Hirata
- William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
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Antol I, Eckert-Maksić M, Müller T, Dallos M, Lischka H. Valence and Rydberg states of protonated formaldehyde. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(03)00770-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Cai ZL, Reimers JR. The First Singlet (n,π*) and (π,π*) Excited States of the Hydrogen-Bonded Complex between Water and Pyridine. J Phys Chem A 2002. [DOI: 10.1021/jp020552z] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zheng-Li Cai
- School of Chemistry, The University of Sydney, NSW 2006, Australia
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LISCHKA H, DALLOS M, SHEPARD R. Analytic MRCI gradient for excited states: formalism and application to the n-π∗ valence- and n-(3s,3p) Rydberg states of formaldehyde. Mol Phys 2002. [DOI: 10.1080/00268970210155121] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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20
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Kumar A, Mishra P. Study of hybridization displacement charge distribution using ab initio wave functions and evaluation of molecular electrostatic properties. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0166-1280(00)00858-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Dallos M, Müller T, Lischka H, Shepard R. Geometry optimization of excited valence states of formaldehyde using analytical multireference configuration interaction singles and doubles and multireference averaged quadratic coupled-cluster gradients, and the conical intersection formed by the 1 [sup 1]B[sub 1](σ-π[sup ∗]) and 2 [sup 1]A[sub 1](π-π[sup ∗]) states. J Chem Phys 2001. [DOI: 10.1063/1.1331107] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Affiliation(s)
- Charles E. Miller
- Department of Chemistry, Haverford College, Haverford, Pennsylvania 19041-1392
| | - Joseph S. Francisco
- Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907-1393
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23
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Density functional calculations on simple carbonyl bases: protonation and hydrogen bond formation with water. Chem Phys 2000. [DOI: 10.1016/s0301-0104(00)00079-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Åstrand PO, Ruud K, Taylor PR. Calculation of the vibrational wave function of polyatomic molecules. J Chem Phys 2000. [DOI: 10.1063/1.480840] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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