Using many-particle basis sets for electronic energy calculations of molecules

1997 ◽  
Vol 38 (3) ◽  
pp. 337-342
Author(s):  
V. P. Morozov ◽  
K. G. Vinogradov
Keyword(s):  
Electronic Energy ◽  
Basis Sets ◽  
Energy Calculations

Electronic Structure Benchmark Calculations of Inorganic and Biochemical Carboxylation Reactions

2018 ◽  
Author(s):  
Oscar A. Douglas-Gallardo ◽  
David A. Sáez ◽  
Stefan Vogt-Geisse ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Electronic Structure ◽  
Chemical Reactions ◽  
Density Functional ◽  
Correlation Energy ◽  
Electronic Energy ◽  
Basis Sets ◽  
Electronic Correlation ◽  
Correct Description ◽  
Carbon Dioxide Co2 ◽  
High Level

<div><div><div><p>Carboxylation reactions represent a very special class of chemical reactions that is characterized by the presence of a carbon dioxide (CO2) molecule as reactive species within its global chemical equation. These reactions work as fundamental gear to accomplish the CO2 fixation and thus to build up more complex molecules through different technological and biochemical processes. In this context, a correct description of the CO2 electronic structure turns out to be crucial to study the chemical and electronic properties associated with this kind of reactions. Here, a sys- tematic study of CO2 electronic structure and its contribution to different carboxylation reaction electronic energies has been carried out by means of several high-level ab-initio post-Hartree Fock (post-HF) and Density Functional Theory (DFT) calculations for a set of biochemistry and inorganic systems. We have found that for a correct description of the CO2 electronic correlation energy it is necessary to include post-CCSD(T) contributions (beyond the gold standard). These high-order excitations are required to properly describe the interactions of the four π-electrons as- sociated with the two degenerated π-molecular orbitals of the CO2 molecule. Likewise, our results show that in some reactions it is possible to obtain accurate reaction electronic energy values with computationally less demanding methods when the error in the electronic correlation energy com- pensates between reactants and products. Furthermore, the provided post-HF reference values allowed to validate different DFT exchange-correlation functionals combined with different basis sets for chemical reactions that are relevant in biochemical CO2 fixing enzymes.</p></div></div></div>

Local-Energy Method in Electronic Energy Calculations

1960 ◽  
Vol 32 (2) ◽  
pp. 313-317 ◽  
Author(s):  
Arthur A. Frost ◽  
Reid E. Kellogg ◽  
Earl C. Curtis
Keyword(s):  
Energy Method ◽  
Electronic Energy ◽  
Local Energy ◽  
Energy Calculations

scholarly journals Ab Initio High-Pressure Study of Semiconductor-Metal Phase Transition of the Chalcogenide Compound KPSe6

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
P. O. Jomo ◽  
C. O. Otieno ◽  
P. W. O. Nyawere
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Ab Initio ◽  
Density Functional ◽  
Basis Sets ◽  
Metal Phase ◽  
Generalized Gradient ◽  
Energy Calculations ◽  
Metal Phase Transition ◽  
Chalcogenide Compound

We report the results of pressure-induced semiconductor-metal phase transition of the semiconducting chalcogenide compound KPSe6 under high pressure using the ab initio methods. The ground-state energy calculations were performed within density functional theory and the generalized gradient approximation using the pseudopotential method with plane-wave basis sets. The projector augmented-wave (PAW) pseudopotentials were used in our calculation. The optimized lattice parameters were found from total energy calculations as 13 Bohr, 1.6 Bohr, and 1.8 Bohr for cell dimensions one, two, and three, respectively, which are in good agreement with experimental calculations. At zero pressure, the material portrayed a semiconducting property with a direct bandgap of ≈1.7 eV. As we subjected the material to pressure, the band gap was observed to reduce until it disappeared. The phase transition from the semiconductor to metal was found to occur at ∼45 GPa, implying that the material underwent metallization as pressure was increased further.

Assessment of the Direct Generalized Bloch Approach B0: Application to the Li and Be Atoms and the Molecules LiH, BeH, and the Phenolate Anion

2005 ◽  
Vol 70 (8) ◽  
pp. 1272-1314
Author(s):  
Holger Meissner
Keyword(s):  
Simple Model ◽  
Configuration Interaction ◽  
Closed Shell ◽  
Experimental Results ◽  
Basis Sets ◽  
Coupled Cluster ◽  
Photoactive Yellow Protein ◽  
Energy Calculations ◽  
Molecular Systems ◽  
Reasonable Approach

Besides the necessity of the development of sophisticated methods to calculate correlation energies - be it the coupled-cluster (CC) or the configuration-interaction (CI) methods and their various approaches - one also accentuate the need for efficient and less demanding methods in the area of medium and large molecular systems. Therefore, this article proposes a computational efficient and in our opinion reasonable approach for the calculation of correlation energies for medium and even larger molecules. This approach, named B0, based on the so-called direct generalized Bloch (DGB) equation which has already been successfully applied to small systems. Within those considerations the B0 approach showed promising results so that further investigations are worthwhile. Here, as a further step in the assessment of this method we apply the B0 approach to the Li and Be atoms as well as the LiH and BeH molecules. Molecules which show open and closed shell characteristics in the equilibrium and in the case of dissociation as well. The results are compared with CC and CI and experimental results if available. Since this results are encouraging even when considering small basis sets and with the prospect of larger molecular systems, therefore, we perform also B0 energy calculations for the low-lying states of the phenolate anion which for instance can be used in a simple model of the photoactive yellow protein (PYP) chromophore.

Medium-Size Polarized Basis Sets Applicability for Interaction Energy Calculations: He2 and Be2 van der Waals Systems

1993 ◽  
Vol 58 (8) ◽  
pp. 1739-1750
Author(s):  
Andrzej Nowek
Keyword(s):  
Interaction Energy ◽  
Van Der Waals ◽  
Basis Set ◽  
Basis Sets ◽  
Medium Size ◽  
Dispersion Energy ◽  
Energy Calculations ◽  
Polarized Basis Sets ◽  
Standard Energy

Polarized bases set approach has been applied for preparation of medium-size contracted GTO basis sets starting from various standard energy-optimized and even-tempered isotropic atomic basis sets. Their usefulness for calculation of the SCF interaction energy and its components as well as dispersion energy consistently determined within the dimer basis set were studied for He2 and Be2 systems for intermediate internuclear separations. The results obtained with polarized basis sets indicate their good performance in comparison with property oriented ones.

Lower bound energy calculations for

1966 ◽  
Vol 62 (4) ◽  
pp. 769-776 ◽  
Author(s):  
Mary Walmsley ◽  
C. A. Coulson
Keyword(s):  
Excited State ◽  
Lower Bound ◽  
Lower Bounds ◽  
Ground State ◽  
Nuclear Charge ◽  
Electronic Energy ◽  
Energy Calculations ◽  
First Excited State

AbstractTwo different calculations are made of lower bounds for the electronic energy of . In the first the method of truncated Hamiltonians due to Bazley and Fox is adapted in such a way that the nuclear charge rather than the energy becomes the eigenvalue. Lower bounds are calculated for the energies of the six lowest σg and six lowest σu states, as well as of the three lowest of both πg and πu symmetries. This approach gives better convergence than when the energy is used as eigenvalue. In the second calculation the method of Temple and Kato is shown to give a satisfactory value for the energy of the ground state, provided that some necessary knowledge of the energy of the first-excited state is available.

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