Berry phase approach to longitudinal dipole moments of infinite chains in electronic-structure methods with local basis sets

2007 ◽  
Vol 126 (23) ◽  
pp. 234101 ◽  
Author(s):  
Konstantin N. Kudin ◽  
Roberto Car ◽  
Raffaele Resta
Keyword(s):  
Electronic Structure ◽  
Berry Phase ◽  
Dipole Moments ◽  
Basis Sets ◽  
Local Basis ◽  
Phase Approach ◽  
Electronic Structure Methods ◽  
Local Basis Sets

Density functional calculations of Ge(105): Local basis sets andO(N)methods

2007 ◽  
Vol 76 (11) ◽  
Author(s):  
T. Miyazaki ◽  
D. R. Bowler ◽  
R. Choudhury ◽  
M. J. Gillan
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Basis Sets ◽  
Local Basis ◽  
Local Basis Sets

Computational investigation of isomeric and conformeric structures of methyl iodoperoxide

2005 ◽  
Vol 83 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Evangelos Drougas ◽  
Agnie M Kosmas
Keyword(s):  
Electronic Structure ◽  
Single Point ◽  
Transition States ◽  
Vibrational Frequencies ◽  
Basis Sets ◽  
Quantum Mechanical ◽  
Energy Structure ◽  
Computational Investigation ◽  
Electronic Structure Methods ◽  
Optimized Geometries

Quantum mechanical electronic structure methods are employed to investigate the isomeric and conformeric stuctures of methyl iodoperoxide. Optimized geometries and harmonic vibrational frequencies are calculated at the MP2 level of theory using two types of basis sets, the 6-311G(d,p) for all atoms and the 6-311G(d,p) combined with the LANL2DZ relativistic ECP procedure for iodine. Refinement of the energetics has been accomplished by performing single-point CCSD(T) calculations. Five isomers were determined in total among which iodomethyl hydroperoxide (ICH2OOH) is found to be the lowest energy structure. Conformational barriers and transition states that connect the isomeric forms have been characterized.Key words: methyl iodoperoxide, isomers, conformers.

On the use of local basis sets for localized molecular orbitals

1980 ◽  
Vol 57 (2) ◽  
pp. 169-178 ◽  
Author(s):  
Hermann Stoll ◽  
Gerhard Wagenblast ◽  
Heinzwerner Preuβ
Keyword(s):  
Molecular Orbitals ◽  
Basis Sets ◽  
Localized Molecular Orbitals ◽  
Local Basis ◽  
Local Basis Sets

scholarly journals Highly accurate local basis sets for large-scale DFT calculations in conquest

2019 ◽  
Vol 58 (10) ◽  
pp. 100503 ◽  
Author(s):  
David R. Bowler ◽  
Jack S. Baker ◽  
Jack T. L. Poulton ◽  
Shereif Y. Mujahed ◽  
Jianbo Lin ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Large Scale ◽  
Basis Sets ◽  
Local Basis ◽  
Local Basis Sets

scholarly journals Assessment of basis sets for F12 explicitly-correlated molecular electronic-structure methods

2009 ◽  
Vol 107 (8-12) ◽  
pp. 963-975 ◽  
Author(s):  
Florian A. Bischoff ◽  
Sandra Wolfsegger ◽  
David P. Tew ◽  
Wim Klopper
Keyword(s):  
Electronic Structure ◽  
Basis Sets ◽  
Molecular Electronic ◽  
Electronic Structure Methods ◽  
Explicitly Correlated ◽  
Molecular Electronic Structure

Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems

2019 ◽  
Author(s):  
Tatiana Woller ◽  
Ambar Banerjee ◽  
Nitai Sylvetsky ◽  
Xavier Deraet ◽  
Frank De Proft ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Basis Set ◽  
Dft Methods ◽  
Molecular Switching ◽  
Wide Range ◽  
Electronic Structure Methods ◽  
Explicitly Correlated ◽  
Relative Errors ◽  
The Stability ◽  
Basis Set Expansion

<p>Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. Taking into account its size and huge conformational flexibility, DFT remains the workhorse for modeling such extended macrocycles. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, p···p stacking, steric effects, ring strain and electron delocalization. As a consequence, the selection of an exchange-correlation functional for describing the energy profile of topological switches is very difficult. For these reasons, we have examined the performance of a variety of wavefunction methods and density functionals for describing the thermochemistry and kinetics of topology interconversions across a wide range of macrocycles. Especially for hexa- and heptaphyrins, the Möbius structures have a pronouncedly stronger degree of static correlation than the Hückel and figure-eight structures, and as a result the relative energies of singly-twisted structures are a challenging test for electronic structure methods. Comparison of limited orbital space full CI calculations with CCSD(T) calculations within the same active spaces shows that post-CCSD(T) correlation contributions to relative energies are very minor. At the same time, relative energies are weakly sensitive to further basis set expansion, as proven by the minor energy differences between MP2/cc-pVDZ and explicitly correlated MP2-F12/cc-pVDZ-F12 calculations. Hence, our CCSD(T) reference values are reasonably well-converged in both 1-particle and n-particle spaces. While conventional MP2 and MP3 yield very poor results, SCS-MP2 and particularly SOS-MP2 and SCS-MP3 agree to better than 1 kcal mol<sup>-1</sup> with the CCSD(T) relative energies. Regarding DFT methods, only M06-2X provides relative errors close to chemical accuracy with a RMSD of 1.2 kcal mol<sup>-1</sup>. While the original DSD-PBEP86 double hybrid performs fairly poorly for these extended p-systems, the errors drop down to 2 kcal mol<sup>-1</sup> for the revised revDSD-PBEP86-NL, again showing that same-spin MP2-like correlation has a detrimental impact on performance like the SOS-MP2 results. </p>

Ideal–Gas Thermochemical Properties for Alkanolamine and Related Species Involved in Carbon Capture Applications

2020 ◽  
Author(s):  
Nayyereh hatefi ◽  
William Smith
Keyword(s):  
Heat Capacity ◽  
Electronic Structure ◽  
Co2 Capture ◽  
Carbon Capture ◽  
Ideal Gas ◽  
Thermochemical Properties ◽  
Temperature Range ◽  
Comparison Results ◽  
Electronic Structure Methods ◽  
Protonated Forms

<div>Ideal{gas thermochemical properties (enthalpy, entropy, Gibbs energy, and heat capacity, Cp) of 49 alkanolamines potentially suitable for CO2 capture applications and their carbamate and protonated forms were calculated using two high{order electronic structure methods, G4 and G3B3 (or G3//B3LYP). We also calculate for comparison results from the commonly used B3LYP/aug-cc-pVTZ method. This data is useful for the construction of molecular{based thermodynamic models of CO2 capture processes involving these species. The Cp data for each species over the temperature range 200 K{1500 K is presented as functions of temperature in the form of NASA seven-term polynomial expressions, permitting the set of thermochemical properties to be calculated over this temperature range. The accuracy of the G3B3 and G4 results is estimated to be 1 kcal/mol and the B3LYP/aug-cc-pVTZ results are of nferior quality..</div>

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>

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