Basis set convergence of binding energy with and without CP-correction utilizing PBE0 method: A benchmark study of X2 (X=Ge, As, Se, Sc, Ti, V, Cr, Mn, Co, Cu, Zn)

2019 ◽  
Vol 18 (08) ◽  
pp. 1950034
Author(s):  
S. Akbudak ◽  
G. Uğur ◽  
Ş. Uğur ◽  
H. Y. Ocak
Keyword(s):  
Binding Energy ◽  
Binding Energies ◽  
Basis Set ◽  
Basis Sets ◽  
Set Convergence ◽  
Hartree Fock ◽  
Counterpoise Correction ◽  
Benchmark Study ◽  
Complete Basis Set ◽  
Speed Up

A DFT study of homonuclear X2 ([Formula: see text], As, Se, Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn) is presented using PBEO exchange (xc) functional which is a mixing of Perdew–Burke–Ernzerhof (PBE) and Hartree Fock (HF) exchange energy. However, we used cc-pVXZ and aug-cc-pVXZ basis sets where X is maximum angular momentum number in basis set. Convergence pattern of binding energy with respect to basis set was observed. Two-point extrapolations to complete basis set (CBS) limit were applied to speed up convergence and decrease the basis set incompleteness error (BSIE). Counterpoise correction (CP) method was utilized to alleviate basis set superposition errors (BSSE). Both CP-corrected and uncorrected binding energies were obtained and compared with the experimental and theoretical binding energy values in literature.

Basis set convergence of the binding energies of strongly hydrogen-bonded atmospheric clusters

2017 ◽  
Vol 19 (2) ◽  
pp. 1122-1133 ◽  
Author(s):  
Jonas Elm ◽  
Kasper Kristensen
Keyword(s):  
Binding Energy ◽  
Molecular Clusters ◽  
Binding Energies ◽  
Basis Set ◽  
Set Convergence ◽  
Atmospheric Clusters ◽  
Hydrogen Bonded

We present the first binding energy benchmark set at the CBS limit of strongly hydrogen bonded atmospheric molecular clusters.

scholarly journals The Search of CH3CN in Interstellar Medium

1970 ◽  
Vol 7 (7) ◽  
pp. 10-14 ◽  
Author(s):  
UP Chaulagain ◽  
B Aryal ◽  
MM Aryal
Keyword(s):  
Binding Energy ◽  
Interstellar Medium ◽  
Flux Density ◽  
Rotational Temperature ◽  
Rotational Frequency ◽  
Basis Set ◽  
Basis Sets ◽  
Color Temperature ◽  
Hartree Fock ◽  
Dust Mass

We present the binding energy, rotational constant, rotational frequency and rotational temperature of CH3CN in different basis sets using Gaussian03. A systematic search of the emission region at 115 GHz is carried out using SkyView Virtual Observatory. A region is selected and studied in the context of rotational temperature of CH3CN using ALADIN2.5 software. From the ab-initio (First principle) calculation of CH3CN in the Hartree Fock level of approximation it is found that there is a strong binding between H, C and N in CH3CN, minimum value of the binding energy being 12.79 eV in the basis set 6-311G which agrees within around 8% to the maximum value of 13.74 eV obtained in the basis set 6-31G*. The estimated value of rotational frequency in the Hartree Fock level of approximation is found to be 322.62 GHz in the basis set 6-31G* which agrees with the values of rotational frequency obtained in other basis sets within around 4%. Similarly, value of rotational temperature in the same basis set 6-31G* is found to be 7.74 K which agrees within around 4% to the corresponding values obtained in other basis sets. The investigation region is a huge (7° × 4°) structure having east to west elongated emission pattern in the CO - survey (115 GHz). We classified this region into three parts (Upper Wing, Lower Wing and Third Region) and study the variation of relative flux density in each pixel. We found that the minimum dust color temperature 8.15 K, 8.04 K and 7.99 K respectively at Upper Wing, Lower Wing and Third Region which are almost 4% differs from rotational temperature CH3CN. This implies that there is strong evidence of possibility of finding CH3CN in the investigated region. But the conformation can only be done by spectral analysis. It is found that the flux density increase from 12 μm to 25 μm and then decreases sharply on moving from 25 μm to 60 μm in the maxima of Upper Wing and Lower wing. The flux density increases but not at significant level when moving from 60 μm to 100 μm. We estimated the dust mass of the three different regions. We found that the mass of Upper Wing, Lower Wing and Third Region are 4273.50 MÈ, 4778.79 Mθ and 2026.75 Mθ respectively. The total mass of the investigated region has to obtain 11079.04 Mθ. The mass of the gas found in the investigated structure is almost 200 times the dust mass. Thus the mass of the investigated structure is found to be 2.22×106 Mθ. Key Words: Interstellar Medium; Flux density; Dust color temperature; Solar mass; Cyanogens. DOI: 10.3126/sw.v7i7.3816 Scientific World Vol.7(7) 2009 pp.10-14

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

scholarly journals Stable Occupancy of Hydrogen Molecules in Clathrate Hydrates and + THF Clathrate Hydrates Determined by Ab Initio Calculations

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Prasad Yedlapalli ◽  
Sangyong Lee ◽  
Jae W. Lee
Keyword(s):  
Ab Initio ◽  
Binding Energies ◽  
Clathrate Hydrates ◽  
Basis Set ◽  
Large Cavity ◽  
Basis Sets ◽  
Pure Hydrogen ◽  
Point Energy ◽  
Small Cavity ◽  
Hydrogen Molecules

Structure II clathrate hydrates of pure hydrogen and binary hydrates of are studied using ab initio calculations to determine the stable occupancies of small cavities. Ab initio calculations are carried out for a double cavity consisting of one dodecahedron (small cavity) and one hexakaidecahedron (large cavity). These two cavities are attached to each other as in sII hydrates to form a double cavity. One or two molecules are placed in the small cavity and one THF (or 4 molecules) molecule is placed in the large cavity. We have determined the binding energies of the double cavities at the MP2 level using various basis sets (3-21G, 3-21G(2p), 3-21 G(2p), 6-31G, 6-31G(2p), and 6-31 G(2p)). Different basis sets yield different stable occupancies of the small cavity. The results from the highest basis set (6-31 G(2p) with zero point energy corrections) indicate that the single occupancy is slightly more favorable than the double occupancy in both the cases of pure hydrates and THF + double hydrates.

Intermolecular π/π and H/π interactions in dimers researched by different computational methods

2014 ◽  
Vol 13 (07) ◽  
pp. 1450057
Author(s):  
Cuihong Wang ◽  
Yue Jiang ◽  
Ruiqin Zhang ◽  
Zijing Lin
Keyword(s):  
High Efficiency ◽  
Dipole Moments ◽  
Binding Energies ◽  
Basis Set ◽  
Theoretical Research ◽  
Basis Sets ◽  
Π Interactions ◽  
Π Stacking ◽  
Structures And Properties ◽  
Satisfactory Precision

The analysis of π/π and H /π interactions in complexes are a challenging aspect of theoretical research. Due to the different approximations of different levels of theory, results tend to be inconsistent. We compared the reliabilities of HF, SVWN, M06L, PW91, BLYP, B3LYP, BHandHLYP, B97D, MP2, and DFTB-D approaches in researching π/π and H /π interactions by calculating the binding energies of five benzene-containing dimers. The effects of 6-31+G**, 6-311++G** and 6-311++G(2df,2p) basis sets on the results were analyzed too. We found that the DFTB-D and B97D methods combined with the 6-311++G** basis set perform well for dimers that contain π/π and H /π interactions. With high efficiency and satisfactory precision, DFTB-D is helpful for the calculation of complexes containing π/π and H /π stacking. We further calculated the structures and properties of phenylalanine-containing dimers using the DFTB-D and B97D methods. The properties of low energy conformers such as rotational constants, dipole moments and molecular orbitals were also analyzed. These data should be helpful for research into systems that contain π/π and H /π stacking.

Potential energy curve of N2 revisited

2011 ◽  
Vol 76 (4) ◽  
pp. 327-341 ◽  
Author(s):  
Vladimír Špirko ◽  
Xiangzhu Li ◽  
Josef Paldus
Keyword(s):  
Potential Energy ◽  
Chem Phys ◽  
Nitrogen Molecule ◽  
Basis Set ◽  
Basis Sets ◽  
Energy Curve ◽  
Vibrational Levels ◽  
Complete Basis Set ◽  
State Potential ◽  
Excellent Description

Recently generated ground state potential energy curves (PECs) for the nitrogen molecule, as obtained with the reduced multireference (RMR) coupled-cluster (CC) method with singles and doubles (RMR-CCSD), and its version corrected for the secondary triples RMR-CCSD(T), using cc-pVXZ basis sets with X = D, T, and Q, as well as the extrapolated complete basis set (cbs) limit (X. Li and J. Paldus: J. Chem. Phys. 2008, 129, 054104), are compared with both the highly accurate theoretical configuration interaction PEC of Gdanitz (Chem. Phys. Lett. 1998, 283, 253) and analytic PECs obtained by fitting an extensive set of experimental data (R. J. Le Roy et al.: J. Chem. Phys. 2006, 125, 164310). These results are analyzed using a morphing procedure based on the reduced potential curve (RPC) method of Jenč. It is found that an RPC fit of both theoretical potentials can be achieved with only a few parameters. The RMR PECs are found to provide an excellent description of experimentally available vibrational levels, but significantly deviate from those of Gdanitz’s PEC for highly stretched geometries, yet still do provide a qualitatively correct PECs that lie within the region delimited by Le Roy’s analytical PECs.

scholarly journals Accurate global potential energy surface for the ground state of CH2+ by extrapolation to the complete basis set limit

RSC Advances ◽  
2018 ◽  
Vol 8 (25) ◽  
pp. 13635-13642 ◽  
Author(s):  
Lu Guo ◽  
Hongyu Ma ◽  
Lulu Zhang ◽  
Yuzhi Song ◽  
Yongqing Li
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ground State ◽  
Energy Surface ◽  
Correlation Energy ◽  
Basis Set ◽  
Basis Sets ◽  
Complete Basis ◽  
Complete Basis Set ◽  
Complete Basis Set Limit

A full three-dimensional global potential energy surface is reported for the ground state of CH2+ by fitting accurate multireference configuration interaction energies calculated using aug-cc-pVQZ and aug-cc-pV5Z basis sets with extrapolation of the electron correlation energy to the complete basis set limit.

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