scholarly journals Origin Invariant Full Optical Rotation Tensor in the Length Dipole Gauge without London Atomic Orbitals

2021 ◽  
Author(s):  
Marco Caricato
Keyword(s):  
Electron Correlation ◽  
Density Functional ◽  
Optical Rotation ◽  
Density Functional Method ◽  
Functional Method ◽  
Basis Set ◽  
Rotation Tensor ◽  
Atomic Orbitals ◽  
Complete Basis Set ◽  
Approximate Wave

<div> <div> <div> <p>We present an origin-invariant approach to compute the full optical rotation tensor (Buckingham/Dunn tensor) in the length dipole gauge without recourse to London atomic orbitals, called LG(OI). The LG(OI) approach is simpler and less computationally demanding than the more common LG-London and modified velocity gauge (MVG) approaches and it can be used with any approximate wave function or density functional method. We report an implementation at coupled cluster with single and double excitations level (CCSD), for which we present the first simulations of the origin-invariant Buckingham/Dunn tensor in the length gauge. With this method, we attempt to decouple the effects of electron correlation and basis set incompleteness on the choice of gauge for optical rotation calculations on simple test systems. The simulations show a smooth convergence of the LG(OI) and MVG results with the basis set size towards the complete basis set limit. However, these preliminary results indicate that CCSD may not be close to a complete description of the electron correlation effects on this property even for small molecules, and that basis set incompleteness may be a less important cause of discrepancy between choices of gauge than electron correlation incompleteness. </p> </div> </div> </div>

scholarly journals Origin Invariant Full Optical Rotation Tensor in the Length Dipole Gauge without London Atomic Orbitals

2021 ◽  
Author(s):  
Marco Caricato
Keyword(s):  
Electron Correlation ◽  
Density Functional ◽  
Optical Rotation ◽  
Density Functional Method ◽  
Functional Method ◽  
Basis Set ◽  
Rotation Tensor ◽  
Atomic Orbitals ◽  
Complete Basis Set ◽  
Approximate Wave

<div> <div> <div> <p>We present an origin-invariant approach to compute the full optical rotation tensor (Buckingham/Dunn tensor) in the length dipole gauge without recourse to London atomic orbitals, called LG(OI). The LG(OI) approach is simpler and less computationally demanding than the more common LG-London and modified velocity gauge (MVG) approaches and it can be used with any approximate wave function or density functional method. We report an implementation at coupled cluster with single and double excitations level (CCSD), for which we present the first simulations of the origin-invariant Buckingham/Dunn tensor in the length gauge. With this method, we attempt to decouple the effects of electron correlation and basis set incompleteness on the choice of gauge for optical rotation calculations on simple test systems. The simulations show a smooth convergence of the LG(OI) and MVG results with the basis set size towards the complete basis set limit. However, these preliminary results indicate that CCSD may not be close to a complete description of the electron correlation effects on this property even for small molecules, and that basis set incompleteness may be a less important cause of discrepancy between choices of gauge than electron correlation incompleteness. </p> </div> </div> </div>

scholarly journals Origin Invariant Optical Rotation in the Length Dipole Gauge without London Atomic Orbitals

2020 ◽  
Author(s):  
Marco Caricato
Keyword(s):  
Density Functional ◽  
Optical Rotation ◽  
Center Of Mass ◽  
Density Functional Method ◽  
Functional Method ◽  
Coupled Cluster ◽  
Atomic Orbitals ◽  
Numerical Tests ◽  
Approximate Wave Function ◽  
Approximate Wave

<div> <div> <div> <p>We present an approach to perform origin-invariant optical rotation calculations in the length dipole gauge without recourse to London atomic orbitals, called LG(OI). The LG(OI) approach works with any approximate wave function or density functional method, but here we focus on the implementation with the coupled cluster (CC) with single and double excitations method because of the lack of production-level alternatives. Preliminary numerical tests show the efficacy of the LG(OI) procedure, and indicate that conventional CC-LG calculations with the origin in the center of mass of a molecule may still carry significant origin dependence. </p> </div> </div> </div>

scholarly journals Origin Invariant Optical Rotation in the Length Dipole Gauge without London Atomic Orbitals

2020 ◽  
Author(s):  
Marco Caricato
Keyword(s):  
Density Functional ◽  
Optical Rotation ◽  
Center Of Mass ◽  
Density Functional Method ◽  
Functional Method ◽  
Coupled Cluster ◽  
Atomic Orbitals ◽  
Numerical Tests ◽  
Approximate Wave Function ◽  
Approximate Wave

<div> <div> <div> <p>We present an approach to perform origin-invariant optical rotation calculations in the length dipole gauge without recourse to London atomic orbitals, called LG(OI). The LG(OI) approach works with any approximate wave function or density functional method, but here we focus on the implementation with the coupled cluster (CC) with single and double excitations method because of the lack of production-level alternatives. Preliminary numerical tests show the efficacy of the LG(OI) procedure, and indicate that conventional CC-LG calculations with the origin in the center of mass of a molecule may still carry significant origin dependence. </p> </div> </div> </div>

A DENSITY FUNCTIONAL THEORY INVESTIGATION ON THE TAUTOMERS AND CRYSTAL OF 2-DIAZO-4,6-DINITROPHENOL

2004 ◽  
Vol 03 (04) ◽  
pp. 599-607 ◽  
Author(s):  
XUE-HAI JU ◽  
HE-MING XIAO
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Lattice Energy ◽  
Functional Method ◽  
Basis Set ◽  
Functional Theory ◽  
Basis Set Superposition Error ◽  
Conduction Bands ◽  
Valence Bands ◽  
Good Agreement

Density functional method was applied to the study of the highly efficient primary explosive 2-diazo-4,6-dinitrophenol (DDNP) in both gaseous tautomers and its bulk state. Two stable tautomers were located. It was found that the structure (I) with open diazo, i.e. with linear CNN, is more stable than that with diazo ring tautomer (II) of DDNP. The structure I is in good agreement with the structure in the bulk. The lattice energy is -89.01 kJ/mol, and this value drops to -83.29 kJ/mol when a 50% correction of the basis set superposition error was adopted. The frontier bands are quite flat. The carbon atoms in DDNP make up the upper valence bands. While the lower conduction bands mainly consist of carbon and diazo N atoms. The bond populations of C–N bonds (both C–Nitro and C–Diazo) are much less than those of the other bonds and the detonation may be initiated through the breakdown of C–N bonds.

scholarly journals Density functional theory study on the molecular structure of loganin

2011 ◽  
Vol 25 (6) ◽  
pp. 287-302 ◽  
Author(s):  
Anoop Kumar Pandey ◽  
Shamoon Ahmad Siddiqui ◽  
Apoorva Dwivedi ◽  
Kanwal Raj ◽  
Neeraj Misra
Keyword(s):  
Molecular Structure ◽  
Density Functional ◽  
Solid Phase ◽  
Density Functional Method ◽  
Functional Method ◽  
Basis Set ◽  
Equilibrium Geometry ◽  
B3lyp Method ◽  
Ft Ir ◽  
Detailed Interpretation

The computational Quantum Chemistry (QC) has been used for different types of problems, for example: structural biology, surface phenomena and liquid phase. In this paper we have employed the density functional method for the study of molecular structure of loganin. The equilibrium geometry, harmonic vibrational frequencies and infrared intensities were calculated by B3LYP/6-311G (d, p) method and basis set combinations. It was found that the optimized parameters obtained by the DFT/B3LYP method are very near to the experimental ones. A detailed conformational analysis was carried out. A detailed interpretation of the infrared spectra of loganin is also reported in the present work. The FT-IR spectra of loganin were recorded in solid phase. The thermodynamic calculations related to the title compound were also performed at B3LYP/6-311G (d, p) level of theory.

Theoretical Study of CN Radicals Chemisorption on the Electronic Properties of BC2N Nanotube

2017 ◽  
Vol 48 ◽  
pp. 38-48 ◽  
Author(s):  
Batoul Makiabadi ◽  
Mohammad Zakarianezhad ◽  
Shahin Mohammadzamani
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Density Functional Method ◽  
Nbo Analysis ◽  
Band Gap Energy ◽  
Functional Method ◽  
Basis Set ◽  
Hybrid Density Functional ◽  
Cn Radicals ◽  
Covalent Nature

In this work, we have investigated the adsorption behavior of the CN radicals on electronic properties of BC2N nanotube (BC2NNT) by means of the B3LYP hybrid density functional method using 6-31G(d) basis set. The results show that CN radicals can be chemically adsorbed on the nanotube. Based on the energy analysis, the most stable position of CN radical on the nanotube is C1 site. Also, the C-side complexes are more stable than the N-side complexes. We investigated the effects of CN radicals adsorption on the electronic properties of the BC2N nanotube. According to our calculations, band gap energy of the BC2NNT decreases with increasing the number of CN radicals. It is predicted that the conductivity and reactivity of nanotube increase by increasing the number of CN radicals. Based on the NBO analysis, in all complexes charge transfer occurs from nanotube to CN radical. The AIM results show that, the Xtube…YCN interaction has covalent nature. Generally, The BC2N nanotube can be used to as sensor for nanodevice applications.

scholarly journals Xrd, Quantum Chemical, Vibrational, Thermal and Antifungal Activity Analysis on 3-Nitroanilinium Hydrogen Oxalate

2019 ◽  
Vol 9 (1S3) ◽  
pp. 319-323
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Basis Set ◽  
Frontier Molecular Orbital ◽  
Geometrical Parameters ◽  
Vibrational Assignments ◽  
Hartree Fock ◽  
Homo Lumo ◽  
Good Agreement

3-nitroanilinium hydrogen oxalate has been crystallized successfully by solvent evaporation method. Optimized molecular geometrical parameters and the vibrational assignments of 3NAOX has been calculated by using Hartree-Fock (HF) and density functional method (B3LYP) with 6-311++G (d, p) basis set. The computational analysis showed good agreement with the experimental data. The energy and various parameters were obtained by HOMO–LUMO plot. The apparent pharmaceutical/biological activity of the salt confirmed by lower band gap value obtain from the Frontier Molecular Orbital (FMO) analysis. Thermal properties of 3NAOX were analyzed by TGA/DTA. The grown crystals were involved in an antimicrobial activity against certain potentially threatening microbes which shows that grown crystal screened the bacteria.

scholarly journals Antioxidant of Trans-Resveratrol: A Comparison between OH and CH Groups Based on Thermodynamic Views

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Thuy Phan Thi ◽  
Son Ninh The
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Basis Set ◽  
Bond Breaking ◽  
Structural Geometry ◽  
Exchange Correlation ◽  
Interesting Compound ◽  
Antioxidative Action ◽  
Bond Disruption

Trans-resveratrol establishes the planarity in its structure which makes it an interesting compound in both experimental and theoretical examinations. The current study, using the density functional method (DFT), attempts to compare the antioxidative capacities between hydroxyl (OH) and aromatic methine (CH) groups of this molecule. Becke’s exchange-correlation B3LYP functional together with 6-311++G(d, p) basis set was used to reveal the effects of structural geometry and electronic feature on the antioxidative results of OH and CH groups. The antioxidative action of trans-resveratrol has followed the HAT mechanism in gas, but the SPLET pathway in liquids. OH bond breaking is easier than CH bond disruption. 4-OH bond breaking induces the lowest BDE values of 74.4–77.9 kcal/mol in gas, acetone, methanol, and water, as well as the lowest PA values of 37.2–46.2 kcal/mol in acetone, methanol, and water. From the kinetic view, 4-OH is also an active center to capture laboratory radical DPPH, ROS radicals HOO• and CH3O•, and RNS radical •NO2.

Density Functional Theory Study of Intermolecular Interaction between RDX and H2O

2013 ◽  
Vol 750-752 ◽  
pp. 1848-1851
Author(s):  
Xiu Lin Zeng ◽  
Xue Hai Ju
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Density Functional Method ◽  
Zero Point ◽  
Functional Method ◽  
Binding Energies ◽  
Basis Set ◽  
Free Energies ◽  
Functional Theory ◽  
Dimerization Process

The density functional method of wB97xD in combination of 6-31+G** basis set was applied to the study of the heterodimers between hexahydro-1,3,5-trinitro-1,3,5-triazine and water. Three stable dimers were located. The binding energies have been corrected for the zero-point vibrational and basis set superposition errors. The largest corrected binding energy is 26.21 kJ/mol. Natural bond orbital analyses and frequency calculations were performed on each optimized structure. The thermodynamic properties of enthalpies, entropies and Gibbs free energies in the dimerization process were presented.

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