Conformational prediction for molecules containing vicinal lone pairs: Basis set studies for H2O2

1977 ◽  
Vol 30 (2) ◽  
pp. 231 ◽  
Author(s):  
PG Burton ◽  
BR Markey
Keyword(s):  
Bond Length ◽  
Bond Angle ◽  
State Of The Art ◽  
Basis Set ◽  
Basis Sets ◽  
Conformational Study ◽  
Gaussian Basis Sets ◽  
Lone Pairs ◽  
Polarization Functions ◽  
Bond Functions

The Dunning and Winter1 (DW) conformational study of H2O2 represents accepted state-of-the-art methodology in accurate SCF computation of molecular properties; nevertheless the prediction of a very short O-O bond length and a very large O-O-H bond angle by DW indicates the difficulty in adequately describing molecules with vicinal lone pairs. Consequently we have reexamined H2O2 with several standard Gaussian basis sets, and in addition have investigated the properties of two further basis set prescriptions. While polarization functions are confirmed to be necessary to attaining the correct H2O2 conformation, the situation of s (and p) Gaussian bond functions in mid-bond positions is shown to be an economical and efficacious alternative to traditional polarizing functions.

Accurate evaluation of SCF and MP2 components of interaction energies. Complexes of HF, OH2, and NH3 with Li+

1988 ◽  
Vol 53 (10) ◽  
pp. 2214-2229 ◽  
Author(s):  
Małgorzata M. Szczęśniak ◽  
Steve Scheiner
Keyword(s):  
Point Charge ◽  
Basis Set ◽  
Basis Sets ◽  
Interaction Energies ◽  
Multipole Moments ◽  
Gaussian Basis Sets ◽  
Basis Set Superposition Error ◽  
Polarization Functions ◽  
Selection Of ◽  
Correlation Corrections

High-quality Gaussian basis sets of the well-tempered type, containing three sets of polarization functions on all atoms, are used to investigate the interaction of Li+ with HF, OH2, and NH3. These sets reproduce the SCF and MP2 energies of the various monomers very well and, moreover, accurately treat the multipole moments and polarizabilities of the monomers. When applied to the complexes, the sets are essentially free of primary and secondary basis set superposition error at the SCF level; MP2 extension effects are also completely negligible while basis set superposition effects are small but non-negligible. Analysis of the correlation corrections to the molecular properties, coupled with comparison of the interaction of the bases with a point charge, provides a straightforward explanation of correlation contributions to the interaction energy. Recommendations are provided to guide selection of basis sets for molecular interactions so as to avoid distortion of the various components.

scholarly journals Theoretical Study of Solvent Effects on the Electronic and Thermodynamic Properties of Tetrathiafulvalene (TTF) Molecule Based on DFT

2021 ◽  
pp. 42-54
Author(s):  
Rabiu Nuhu Muhammad ◽  
N. M. Mahraz ◽  
A. S Gidado ◽  
A. Musa
Keyword(s):  
Thermodynamic Properties ◽  
Bond Length ◽  
Density Functional ◽  
Theoretical Study ◽  
Energy Gap ◽  
Basis Set ◽  
Basis Sets ◽  
Frontier Molecular Orbital ◽  
Orbital Energy ◽  
Chemical Hardness

Tetrathiafulvalene () is an organosulfur compound used in the production of molecular devices such as switches, sensors, nonlinear optical devices and rectifiers. In this work, a theoretical study on the effects of solvent on TTF molecule was investigated and reported based on Density Functional Theory (DFT) as implemented in Gaussian 03 package using B3LYP/6-31++G(d,p) basis set. Different solvents were introduced as a bridge to investigate their effects on the electronic structure. The HUMO, LUMO, energy gap, global chemical index, thermodynamic properties, NLO and DOS analysis of the TTF molecule in order to determine the reactivity and stability of the molecule were obtained. The results obtained showed that the solvents have effects on the electronic and non-linear-optical properties of the molecule. The optimized bond length revealed that the molecule has strong bond in gas phase with smallest bond length of about 1.0834Å than in the rest of the solvents. It was observed that the molecule is more stable in acetonitrile with HOMO-LUMO gap and chemical hardness of 3.6373eV and 1.8187eV respectively. This indicates that the energy gap and chemical hardness of TTF molecule increases with the increase in polarity and dielectric constant of the solvents. The computed results agreed with the results in the literature. The thermodynamics and NLO properties calculation also indicated that TTF molecule has highest value of specific heat capacity (Cv), total dipole moment () and first order hyperpolarizability () in acetonitrile, while acetone has the highest value of entropy and toluene has a slightly higher value of zero point vibrational energy (ZPVE) than the rest of the solvents. The results show that careful selection of the solvents and basis sets can tune the frontier molecular orbital energy gap of the molecule and can be used for molecular device applications.

Polarization consistent basis sets using the projector augmented wave method: a renovation brought by PAW into Gaussian basis sets

2020 ◽  
Vol 22 (46) ◽  
pp. 27037-27052
Author(s):  
Quan Manh Phung ◽  
Masaya Hagai ◽  
Xiao-Gen Xiong ◽  
Takeshi Yanai
Keyword(s):  
Dft Calculations ◽  
Basis Set ◽  
Basis Sets ◽  
Wave Method ◽  
Gaussian Basis Sets ◽  
New Family ◽  
Consistent Basis ◽  
Projector Augmented Wave

A new family of polarization consistent basis set, combined with the projector augmented wave method, was introduced. The basis sets are compact and have good performance as compared to conventional all-electron basis sets in DFT calculations.

Universal Gaussian basis functions in relativistic quantum chemistry: atomic Dirac–Fock–Coulomb and Dirac–Fock–Breit calculations

1992 ◽  
Vol 70 (6) ◽  
pp. 1822-1826 ◽  
Author(s):  
G. L. Malli ◽  
A. B. F. Da Silva ◽  
Yasuyuki Ishikawa
Keyword(s):  
Relativistic Quantum ◽  
Basis Set ◽  
Basis Sets ◽  
Interaction Energies ◽  
Gaussian Basis Sets ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Gaussian Basis Set ◽  
Good Agreement

Matrix Dirac–Fock–Coulomb and Dirac–Fock–Breit self-consistent field calculations are performed for a number of neutral atoms. He (Z = 2) through Xe (Z = 54), using the universal Gaussian basis set (18s, 12p, 11d) reported recently by Da Silva etal. The total Dirac–Fock–Coulomb, the Dirac–Fock–Breit, and the Breit interaction energies calculated with this universal Gaussian basis set are in good agreement with the corresponding values obtained by using an extensive well-tempered Gaussian basis set for the He through Ca (Z = 20) atoms. Although this universal Gaussian basis set is inadequate for the calculation of total Dirac–Fock–Coulomb and Dirac–Fock–Breit energies for the Kr, Sr, and Xe atoms, the Breit interaction energies calculated with this basis for these three atoms are in very good agreement with the corresponding Breit interaction energies obtained by using the extensive well-tempered Gaussian basis sets. Work is in progress to generate a more extensive and energetically better universal Gaussian basis set for He through Xe for its use in non-relativistic Hartree–Fock as well as Dirac–Fock self-consistent field calculations on polyatomics involving heavy atoms.

A GTO basis set calculation of properties of the continuum. Photoionization and resonances of He

1992 ◽  
Vol 70 (2) ◽  
pp. 513-519 ◽  
Author(s):  
Roberto Moccia ◽  
Pietro Spizzo
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Photoionization Cross Section ◽  
Basis Set ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Continuum States ◽  
K Matrix ◽  
The Continuum ◽  
Autoionizing States

By using the K-matrix technique for the continuum states that was previously employed with particularly diffuse L2 basis sets, it is shown that GTO bases are also capable of yielding accurate values for the properties belonging to the electronic continuum. The method has been tested for helium and proved of satisfactory accuracy also for the analysis of the autoionizing states. The results include the phase shifts of the continuum states of the 1Seand 1P° manifolds, the properties of the lowest resonances of these symmetries, the ground state photoionization cross section, and the S contribution to the 1s2p1P° photoionization cross section. The results obtained suggest that the proposed technique should be useful for computing molecular differential photoionization cross sections by exploiting the widely used codes that employ GTO bases. Keywords: photoionization, Gaussian basis sets, helium, autoionizing states.

Accurate ab initio Calculations of Methane Dimer Interaction Energies and Molecular Dynamics Simulation of Fluid Methane

2009 ◽  
Vol 1177 ◽  
Author(s):  
Arvin Huang-Te Li ◽  
Sheng Der Chao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Binding Energy ◽  
Ab Initio ◽  
Bond Length ◽  
Dynamics Simulation ◽  
Basis Set ◽  
Basis Sets ◽  
Equilibrium Bond Length ◽  
Basis Size

AbstractIntermolecular interaction potentials of the methane dimers have been calculated for 12 symmetric conformations using the Hartree-Fock (HF) self-consistent theory, the second-order M�ller-Plesset (MP2) perturbation theory, and the coupled-cluster with single and double and perturbative triple excitations (CCSD(T)) theory. The HF calculations yield unbound potentials largely due to the exchange-repulsion interaction. In MP2 and CCSD(T) calculations, the basis set effects on the repulsion exponent, the equilibrium bond length, the binding energy, and the asymptotic behavior of the calculated intermolecular potentials have been thoroughly studied. We have employed basis sets from the Slater-type orbitals fitted with Gaussian functions, Pople�s medium size basis sets to Dunning�s correlation consistent basis sets. With increasing basis size, the repulsion exponent and the equilibrium bond length converge at the 6-31G** basis set and the 6-311++G(2d, 2p) basis set, respectively, while a large basis set (aug-cc-pVTZ) is required to converge the binding energy at a chemical accuracy (˜0.01 kcal/mol). We used the BSSE corrected results that systematically converge to the destined potential curve with increasing basis size. The binding energy calculated and the equilibrium bond length using the CCSD(T) method are close to the results at the basis set limit. For molecular dynamics simulation, a 4-site potential model with sites located at the hydrogen atoms was used to fit the ab initio potential data. This model stems from a hydrogen-hydrogen repulsion mechanism to explain the stability of the dimer structure. MD simulations using the ab initio PES show good agreement on both the atom-wise radial distribution functions and the self-diffusion coefficients over a wide range of experimental conditions.

Experimental Gas Phase 1H NMR Spectra and Basis Set Dependence of ab initio GIAOMO Calculations of 1H and 13C NMR Absolute Shieldings and Chemical Shifts of Small Hydrocarbons

2004 ◽  
Vol 59 (10) ◽  
pp. 1153-1176 ◽  
Author(s):  
Thomas Zuschneid ◽  
Holger Fischer ◽  
Thomas Handel ◽  
Klaus Albert ◽  
Günter Häfelinger
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Basis Set ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Phase Measurements ◽  
H Nmr ◽  
Set Up

AbstractHigh-resolution gas phase measurements of 1H NMR spectra at 400 MHz and atmospheric pressure of seven small hydrocarbons are presented. The developed new method and the experimental set-up are described. Ab initio GIAO MO calculations of 1H and 13C NMR absolute shieldings on the HF, MP2 and B3LYP levels using 25 standard gaussian basis sets are reported for these hydrocarbons, based on experimental re distances. The measured gas phase 1H chemical shifts have been converted to an absolute σ0 shielding scale by use of the literature shielding of methane. These and gas phase 13C literature values have been transferred with literature ZPV data to estimated σeexp shieldings which are used to evaluate the basis set dependence of the calculated σe shieldings utilizing linear least squares regressions. Exponential extrapolations of Dunning basis set calculations allow the determination of basis set limits for 1H and 13C shieldings. 1H and 13C chemical shifts have been derived from the HF calculated shieldings with shieldings of TMS which has been geometry optimized and GIAO calculated in each basis. Standard deviations (esd) as low as 0.09 ppm for 1H and 0.76 ppm for 13C calculations have been obtained.The statistically best basis set for simultaneous calculation of 1H and 13C absolute shieldings or relative shifts is 6-311G* within the HF and B3LYP methods. Aiming for highest accuracy and precision, 1H and 13C have to be treated separately. In this case, best results are obtained using MP2/6-311G** or higher for 1H shieldings and MP2/cc-pVTZ for 13C shieldings.

Application of numerical basis sets with a family of DFT methods to predict the transition states of Diels-Alder reactions: Assessing the accuracy through synchronous transit method

2017 ◽  
Author(s):  
Saurav Dutta ◽  
Bhabani S. Mallik
Keyword(s):  
Transition State ◽  
Alder Reaction ◽  
Diels Alder ◽  
Computational Method ◽  
Basis Set ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Dft Methods ◽  
Diels Alder Reaction ◽  
Transition State Search

<div> <table> <tr> <td> <p>Knowledge of the transition state is crucial in determining the mechanism in order to diversify the applicability of the reaction. The computational method is the most convenient way to locate the transition state in the absence any efficient experimental technique. We have applied the method of the transition state search on the Diels-Alder reaction computationally by means of combined linear synchronous transit and quadratic synchronous transit methods. Here we have shown that, of various methods adopted, BOP functional with numerical basis set provides a computationally economical alternative to the widely used B3LYP functional with higher Gaussian basis sets in the transition state search. It can reproduce the experimental parameters like activation energy of the Diels-Alder reaction, and the calculations are much faster than the corresponding other functional based calculations.</p> </td> </tr> </table> </div>

scholarly journals Quantum Mechanical Study of YTiO3 to the Investigation of Piezoelectricity

2011 ◽  
Vol 2011 ◽  
pp. 1-5
Author(s):  
Raimundo Dirceu de Paula Ferreira ◽  
Marcos Antonio Barros dos Santos ◽  
Maycon da Silva Lobato ◽  
Jardel Pinto Barbosa ◽  
Marcio de Souza Farias ◽  
...  
Keyword(s):  
Total Energy ◽  
Piezoelectric Properties ◽  
Piezoelectric Effect ◽  
Basis Set ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Generator Coordinate ◽  
Mechanical Study ◽  
Quantum Mechanical Study

In previous articles we reported through theoretical studies the piezoelectric effect in BaTiO3, SmTiO3, and YFeO3. In this paper, we used the Douglas-Kroll-Hess (DKH) second-order scalar relativistic method to investigate the piezoelectricity in YTiO3. In the calculations we used the [6s4p] and [10s5p4d] Gaussian basis sets for the O (3P) and Ti (5S) atoms, respectively, from the literature in combination with the (30s21p16d)/[15s9p6d] basis set for the Y (3D) atom, obtained by generator coordinate Hartree-Fock (GCHF) method, and they had their quality evaluated using calculations of total energy and orbital energies (HOMO and HOMO-1) of the 2TiO+1 and 1YO+1 fragments. The dipole moment, the total energy, and the total atomic charges in YTiO3 in Cs space group were calculated. When we analyze those properties we verify that it is reasonable to believe that YTiO3 does not present piezoelectric properties.

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