scholarly journals The basis set effect on the results of the minimization of the total energy bifunctionalE[?A,?B]

2004 ◽  
Vol 101 (5) ◽  
pp. 543-549 ◽  
Author(s):  
Marcin Dulak ◽  
Tomasz A. Wesolowski
Keyword(s):  
Total Energy ◽  
Basis Set ◽  
Basis Set Effect

Inelastic scattering of interstellar silyl cyanide (SiH3CN) by helium atoms : cross-sections and rate coefficients for A- and E-SiH3CN

2021 ◽  
Vol 507 (4) ◽  
pp. 5264-5271
Author(s):  
Manel Naouai ◽  
Abdelhak Jrad ◽  
Ayda Badri ◽  
Faouzi Najar
Keyword(s):  
Inelastic Scattering ◽  
Total Energy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Explicitly Correlated ◽  
Correlation Consistent ◽  
Triple Excitation

ABSTRACT Rotational inelastic scattering of silyl cyanide (SiH3CN) molecule with helium (He) atoms is investigated. Three-dimensional potential energy surface (3D-PES) for the SiH3CN–He interacting system is carried out. The ab initio 3D-PES is computed using explicitly correlated coupled cluster approach with single, double, and perturbative triple excitation CCSD(T)-F12a connected to augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. A global minimum at (R = 6.35 bohr; θ = 90○; ϕ = 60○) with a well depth of 52.99 cm−1 is pointed out. Inelastic rotational cross-sections are emphasized for the 22 first rotational levels for total energy up to 500 cm−1 via close coupling (CC) approach in the case of A-SiH3CN and for the 24 first rotational levels for total energy up to 100 cm−1 via CC and from 100 to 500 cm−1 via coupled states (CS) in the case of E-SiH3CN. Rate coefficients are derived for temperature until 80 K for both A- and E-SiH3CN–He systems. Propensity rules are obtained for |ΔJ| = 2 processes with broken parity for A-SiH3CN and for |ΔJ| = 2 processes with |ΔK| = 0 and unbroken parity for E-SiH3CN.

scholarly journals Thermodynamic investigation of promethazine, loratadine, cetirizine and buclizine as antihistamine drugs; monte carlo and semi-empirical studies

2020 ◽  
Vol 33 (01) ◽  
pp. 94-108
Author(s):  
Mina Zakeri ◽  
Majid Monajjemi ◽  
Ali Ebrahimi
Keyword(s):  
Total Energy ◽  
Frequency Analysis ◽  
Empirical Studies ◽  
Zero Point ◽  
Heat Of Formation ◽  
Electronic Energy ◽  
Basis Set ◽  
Amber Force Field ◽  
Environment Temperature ◽  
Semi Empirical

In this article, we discussed about four antihistamine drug called promethazine, loratadine, cetirizine and buclizine. Promethazine in this list is the only one in first generation antihistamine classification with CNS sedation effect and the other three belongs to second generation antihistamine group which are non-sedation and used to treat in many different anti-allergenic fields. In the following we optimized potential, kinetic and total energy of these molecules at body temperature (310 k˚) and environment temperature (298 k ˚) using Mont Carlo method in Amber force field in 500 ns. The quantum mechanics calculations and molecular structure of these molecules investigated using B3LYP level of theory with 6-31 G (d) as a basis set. Theoretical computations were performed to study thermodynamic parameters and frequency analysis. Electronic, thermal, zero point and gibs free energy and enthalpy were estimated in frequency analysis. Semi empirical computations were summarized to pm3 method and different energy parameters (total energy, Binding Energy, Isolated Atomic Energy, Electronic Energy, Core–Core Interaction and Heat of Formation.

The Effects of Split Valence Basis Sets on Muon Hyperfine Interaction in Guanine Nucleobase and Nucleotide Structures

2019 ◽  
Vol 966 ◽  
pp. 222-228 ◽  
Author(s):  
Wan Nurfadhilah Zaharim ◽  
Shukri Sulaiman ◽  
Siti Nuramira Abu Bakar ◽  
Nur Eliana Ismail ◽  
Harison Rozak ◽  
...  
Keyword(s):  
Total Energy ◽  
Hyperfine Interactions ◽  
Phosphate Group ◽  
Basis Set ◽  
Basis Sets ◽  
Cluster Method ◽  
Sugar Phosphate ◽  
Atomic Orbitals ◽  
Fermi Contact ◽  
Triple Zeta

The DFT cluster method was employed to investigate the electronic structures and muonium hyperfine interactions in guanine nucleobase and nucleotide using three different basis sets. The total energy and Fermi contact values were calculated for muon trapped at carbon '8'. The three basis sets, 6-31G, 6-311G and 6-311G(d,p), were used in tandem with the B3LYP functional. There are significant quantitative differences in the calculated total energy. 6-311G(d,p) produced the lowest total energy as compared to the other basis sets. The lowering of the total energy is due to the increase in the number of basis functions to describe the atomic orbitals, which is consistent with the postulate on basis set completeness. The 6-31G basis set produced the muon Fermi contact value that is the closest to the experimental value. The calculated Fermi contact values for the nucleobase and nucleotide are significantly lowered in going from the double-zeta to the triple-zeta basis set by 5% and 4% respectively. The lowering of the Fermi contact value can be attributed to the extension of the triple-zeta basis set in describing the valence atomic orbitals. The presence of the sugar phosphate group in the nucleotide instead of the methyl group tends to lower the Fermi contact value. Thus, the sugar phosphate group should be taken into consideration when designing a calculation model.

The application of an optimization technique to the development of universal basis sets

1992 ◽  
Vol 70 (2) ◽  
pp. 580-588 ◽  
Author(s):  
R. Custodio ◽  
J. D. Goddard ◽  
M. Giordan ◽  
N. H. Morgon
Keyword(s):  
Total Energy ◽  
Energy Criterion ◽  
Basis Set ◽  
Basis Sets ◽  
Weight Functions ◽  
Statistical Criterion ◽  
Minimum Total Energy ◽  
Discretization Technique ◽  
Universal Bases ◽  
Molecular Calculations

The Simplex method was used to define atomic and universal meshes using the integral discretization technique for the Griffin–Hill–Wheeler-Hartree–Fock equations. This technique represents a basis set as an exponential set of the form:[Formula: see text]For atoms, the minimum total energy criterion was employed. For the universal basis, three different procedures were tested: (a) defining the universal basis using information on the isolated atoms, (b) determining the universal Ω0(k) through atomic calculations and reoptimizing the ΔΩ(k) for different symmetries employing simultaneously a single atomic calculation as a reference point, and (c) optimizing the universal mesh using a statistical criterion such as the squares of the deviations of the total energy. The meshes obtained by the minimum total energy criterion or the squares of deviations of the total energy for the universal basis are accurate for the total energy but the weight functions are deficient in the valence region. Shifting the optimized Ω0(k) to [Formula: see text], fixing [Formula: see text], and reoptimizing ΔΩ(k) for each symmetry species produces a better description of weight functions at the expense of a less accurate total energy. In general, no significant statistical difference was observed for the various universal bases generated by procedures (a) and (b) or by (c) provided the shift correction was made to the latter. Application of these bases to diatomic molecules (N2, CO, P2, CS) showed that the universal bases are as accurate as those optimized for atomic systems. If the bases are transferred from atoms to molecules, the shift corrections to the weight functions of the atoms are not useful in molecular calculations. The almost equivalent molecular properties and the good total energies show that the best basis for molecular calculations is that optimized by procedure (c). Keywords: universal basis sets, integral discretization technique.

scholarly journals Synthesis, Spectroscopic Investigation and Computational Studies of 2-Formyl-4-(Phenyldiazenyl)Phenyl Methyl Carbonate and 4-((4-Chlorophenyl)Diazenyl)-2-Formylphenyl Methyl Carbonate

2016 ◽  
Vol 66 ◽  
pp. 38-70 ◽  
Author(s):  
A. Arokiasamy ◽  
G. Manikandan ◽  
V. Thanikachalam ◽  
K. Gokula Krishnan
Keyword(s):  
Total Energy ◽  
Density Functional ◽  
Vibrational Energy ◽  
Zero Point ◽  
Basis Set ◽  
Stable Configuration ◽  
Vibrational Assignments ◽  
Computational Optimization ◽  
Methyl Carbonate ◽  
Surface Scan

Two new compounds namely 2-formyl-4-(phenyldiazenyl)phenyl methyl carbonate (FPMC) and 4-((4-chlorophenyl) diazenyl)-2-formylphenyl methyl carbonate (CFPMC) have been synthesized and have characterized using FT-IR, FT-Raman,1H and13C NMR techniques. Computational optimization studies have been carried out using Hatree–Fock (HF) and Density Functional Theory (DFT–B3LYP) methods with 6–31+G(d, p) basis set ofGaussian 09Wsoftware. The stable configuration of the title compounds were achieved theoretically by potential energy surface scan analysis. The complete vibrational assignments were performed on the basis of total energy distribution (TED) and natural bonding orbital (NBO) have been studied. Various parameters such as EHOMO, ELUMO,total energy, dipole moment, polarizability, first order hyperpolarizability, zero–point vibrational energy as well as thermal properties were analyzed and reported for the title compounds.

scholarly journals On the Basis Set Selection for Calculations of Core-Level States: Different Strategies to Balance Cost and Accuracy

2020 ◽  
Author(s):  
Ronit Sarangi ◽  
Marta L. Vidal ◽  
Sonia Coriani ◽  
Anna Krylov
Keyword(s):  
Chem Phys ◽  
Core Level ◽  
Virtual Space ◽  
Basis Set ◽  
Basis Sets ◽  
The Core ◽  
Basis Set Effect ◽  
Mixed Precision ◽  
Selection For ◽  
Standard Strategy

<p>We present a study on basis set effect in correlated calculations of core-level states. While it is well recognized that the core-level states require using more extensive basis sets than their valence counterparts, the standard strategy has been to use large contracted basis sets, such as the cc-pVXZ or cc-pCXZ series. Building upon the ideas of Besley, Gilbert, and Gill [J. Chem. Phys. 130, 124308 (2009)], we show that much more effective strategy is to use uncontracted bases, such as core or fully uncontracted Pople's basis. The physical grounds behind this approach are explained and illustrated by numerical results. We also discuss other cost-saving strategies, such as virtual space truncation and using mixed precision execution.</p>

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