Case Study in a Conceptual DFT Investigation of New Corrosion Inhibitor

Inhibition efficiency of thiosemicarbazide derivative, namely 4-ethyl-1-(4-oxo-4-phenylbutanoyl)thiosemicarbazide (EOPT) on corrosion of mild steel, was investigated utilizing the density functional theory (DFT) modeling techniques in the aqueous phase. Chemical parameters at the quantum level, such as energies of highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), dipole moment (µ), absolute electronegativity (χ), global hardness (η), softness (σ), and the fraction of electrons transferred (∆N) have been determined at the B3LYP level of theory with 6-31G (d, p) basis set.

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A Preliminary First Principle Study on Photochromism of Diarylethene Molecules

Prithvi Journal of Research and Innovation ◽

10.3126/pjri.v1i0.29891 ◽

2019 ◽

Vol 1 ◽

pp. 67-77

Author(s):

Ravi Karki

Keyword(s):

Molecular Orbital ◽

Density Functional ◽

Energy Difference ◽

Basis Set ◽

Functional Theory ◽

Solvation State ◽

Highest Occupied Molecular Orbital ◽

Lowest Unoccupied Molecular Orbital ◽

Energy Consideration ◽

Hybrid Density Functional

Photochromism in some diarylethene molecules have been studied by using hybrid density functional theory using the ground state energy consideration. In particular, B3LYP functional and all electron basis set 6-311G (2d,2p) as implemented in Gaussian09 suites of program has been used to investigate the energy difference of two stable isomers of stilbene, azobenzene, cyclooctane, and 1,2, dimethylcyclohexane molecules. The energy difference is corroborated to calculate the frequencies of photons that are required to induce photochromism in these molecules in vacuum and in solvation state. The study found that the molecules exhibit photochromism at various frequency range from infra-red to ultraviolet. The binding energy per atom, charge distribution, HOMO-LUMO (Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital) gap are also calculated for all the molecules in vacuum, water and ethanol solvent. The results obtained are in accordance with the experimental observations.

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Structural, QTAIM, thermodynamic properties, bonding, aromaticity and NMR analyses of cation–π interactions of mono and divalent metal cations (Li+, Na+, K+, Be2+, Mg2+, and Ca2+) with substituted pyrazine derivatives

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633615500443 ◽

2015 ◽

Vol 14 (06) ◽

pp. 1550044 ◽

Cited By ~ 4

Author(s):

Maryam Zaboli ◽

Heidar Raissi

Keyword(s):

Molecular Orbital ◽

Density Functional ◽

Chemical Potential ◽

Basis Set ◽

Chemical Hardness ◽

Aromatic Rings ◽

Functional Theory ◽

Highest Occupied Molecular Orbital ◽

Polarized Continuum Model ◽

Lowest Unoccupied Molecular Orbital

Theoretical investigation of 42 cation-π complexes formed by the alkali metal ( Li +, Na +, K +), alkaline-earth cations ( Be 2+, Mg 2+, Ca 2+) and π-system of the pyrazine and its derivatives have been performed at density functional theory (DFT) (B3LYP functional) and MP2 methods with 6-311++G** basis set in the gas phase and the polarized continuum model (PCM)-water solvation. The following substituents have been taken into consideration: Br , Cl , CH 3, OH , OCH 3 and SH . The interactions present in these complexes have been investigated by means of the natural bond orbital (NBO) and the Bader's quantum theory of atoms in molecules (QTAIMs) approaches. The effects of the interactions on NMR data have been probed using the GIAO-based method to extend investigation of the studied compounds. The calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies show that charge transfer occurs within each complex. Vibrational frequencies and physical properties such as dipole moment, chemical potential, chemical hardness and chemical electrophilicity of these compounds have been systematically explored. The aromaticity of aromatic rings has been measured using several well-established indices of aromaticity such as nucleus-independent chemical shift, harmonic oscillator models of the aromaticity, para-delocalization index, average two-center indices, aromatic fluctuation index and π-fluctuation aromatic index.

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Cross-conjugation as a Motif for Organic Non-Linear Optical Molecules

MRS Proceedings ◽

10.1557/opl.2014.793 ◽

2014 ◽

Vol 1698 ◽

Author(s):

Meghana Rawal ◽

Kerry Garrett ◽

Andreas F. Tillack ◽

Werner Kaminsky ◽

Evgheni Jucov ◽

...

Keyword(s):

Molecular Orbital ◽

Density Functional ◽

Dipole Moments ◽

X Ray Diffraction ◽

Conjugated Molecules ◽

Functional Theory ◽

Highest Occupied Molecular Orbital ◽

Donor And Acceptor ◽

Vis Spectroscopy ◽

Lowest Unoccupied Molecular Orbital

ABSTRACTWe studied the effect of a cross-conjugated bridging group (χC) on charge-transfer in a push-pull chromophore system. The hyperpolarizability of such molecules was found to be comparable to that of a fully π-conjugated molecule (πC) with the same donor and acceptor. The cross-conjugated moiety was then applied as a pendant to a fully π-conjugated chromophore containing a tricyanopyrroline acceptor (TCP). The addition of a χC moiety did not alter the intrinsic hyperpolarizability and provides an avenue for extending and aiding πC systems. The molecules were examined by X-ray diffraction (XRD), hyper-Raleigh scattering (HRS) and UV-visible (UV-vis) spectroscopy. Experimental results were compared with the predictions of density functional theory (DFT). Cross-conjugated molecules have comparable β values, relative to πC molecules, due to reduced spatial overlap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). Thus, the χC architecture could facilitate independent modification of donor and acceptor strengths while minimizing unfavorable effects on electronic transitions and dipole moments.

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Density Functional Theory Study of CL-20/Nitroimidazoles Energetic Cocrystal Compounds in an External Electric Field

10.21203/rs.3.rs-768607/v1 ◽

2021 ◽

Author(s):

xiaosong Xu ◽

Renfa Zhang ◽

Wenxin Xia ◽

Peng Ma ◽

Congming Ma ◽

...

Keyword(s):

Density Functional Theory ◽

Electric Field ◽

Nitro Group ◽

External Electric Field ◽

Molecular Orbital ◽

Density Functional ◽

Energy Gap ◽

Functional Theory ◽

Highest Occupied Molecular Orbital ◽

Lowest Unoccupied Molecular Orbital

Abstract The external electric field has a significant influence on the sensitivity of the energetic cocrystal materials. In order to find out the relationship between the external electric field and sensitivity of energetic cocrystal compounds 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-2,4-dinitro-1H-imidazole (CL-20/2,4-MDNI) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-4,5-dinitro-1H-imidazole (CL-20/4,5-MDNI). In this work, density functional theory (DFT) at B3LYP-D3/6-311+G(d,p) and M062X-D3/ma-def2 TZVPP levels was employed to calculate the bond dissociation energies (BDEs) of selected N-NO2 trigger bonds, frontier molecular orbitals, electrostatic potentials (ESPs) and nitro group charges (QNO2) under different external electric field. The results show that as the positive electric field intensity increases, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy gap and BDEs become smaller, and the local positive ESPs becomes larger, so that the energetic cocrystals tends to have higher sensitivity. In addition, the linear fitting results show that the trigger bond length and nitro group charge changes are closely related to the external electric field strength.

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Crystal Structure, Hirshfeld Surface and Frontier Molecular Orbital Analyses of N-[2-(trifluoromethyl)phenyl]succinamic Acid

Asian Journal of Chemistry ◽

10.14233/ajchem.2020.22860 ◽

2020 ◽

Vol 32 (12) ◽

pp. 3179-3185

Author(s):

P.A. Suchetan ◽

S. Naveen ◽

N.K. Lokanath ◽

P. Krishna Murthy ◽

M.V. Deepa Urs

Keyword(s):

Hydrogen Bonds ◽

Molecular Orbital ◽

Density Functional ◽

Hirshfeld Surface ◽

Basis Set ◽

Frontier Molecular Orbital ◽

Reactivity Descriptors ◽

Succinamic Acid ◽

Highest Occupied Molecular Orbital ◽

Lowest Unoccupied Molecular Orbital

The ortho-CF3 substituent and the N-H bond are in syn-conformation in N-[2-(trifluoromethyl)phenyl]succinamic acid. In amide and acid functionalities, the carbonyl groups are directed in opposite directions to each other and their related-CH2 groups. syn-Conformation is observed for the acid functionality, where the carbonyl C=O and hydroxyl O-H bonds are directed in the same direction. Three planar fragments comprise of the molecule: aromatic ring (A), core portion -Carm-N(H)-C(=O)-C(H2)-C(H2)(B) and -C(H2)-C(=O)-OH(C). The dihedral angle between a pair of fragments being 48.6(4)º (A and B), 81.6 (4)º (B and C) and 70.5 (5)º (A and C). N-H•••O hydrogen bonds bind the molecules forming C(4) chains in the crystal, and the neighbouring anti-parallel chains are bound by O-H•••O hydrogen bonds resulting in a chair shaped ribbon of one-dimensional nature. The Hirshfeld surface study was carried out, including fingerprint plots. Studies have shown that the interactions with O•••H/H•••O (27.4%), H•••H (27.3%) and H•••F/F•••H (20.2%) substantially added to the surface. Theoretically, the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and various global reactivity descriptors were also computed by the density functional theory (DFT/B3LYP) approach with a 6-311G(d, p) basis set in the ground state on the geometrically optimized structure in the gas phase.

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Relationship between the Electrical Characteristics of Molecules and Fast Streamers in Ester Insulation Oil

International Journal of Molecular Sciences ◽

10.3390/ijms21030974 ◽

2020 ◽

Vol 21 (3) ◽

pp. 974 ◽

Cited By ~ 1

Author(s):

Kaizheng Wang ◽

Feipeng Wang ◽

Ziyi Lou ◽

Qiuhuang Han ◽

Qi Zhao ◽

...

Keyword(s):

Molecular Orbital ◽

Density Functional ◽

Ester Group ◽

Electrical Characteristics ◽

Functional Theory ◽

Highest Occupied Molecular Orbital ◽

Lightning Impulse ◽

Lowest Unoccupied Molecular Orbital ◽

Natural Ester ◽

Insulation Oil

The effects of C=C, ester and β-H groups on the ionization potential (IP) and electron affinity (EA) of molecules in natural ester insulation oil were investigated by density functional theory (DFT). The major contribution to the highest occupied molecular orbital (HOMO) comes from the carbon atoms adjacent to C=C. Thus, the IPs of triglycerides decrease as the number of C=C double bonds increases. The C=C in alkanes may also lower the IP. However, the β-H in triglycerides has little effect on the IP, and C=C and β-H have only a small effect on the EAs of the triglycerides because of the major contributions of atoms near the ester group in triglycerides to the lowest unoccupied molecular orbital (LUMO). This study calculated the IPs of 53 kinds of molecules in FR3, which are significantly lower compared with those of molecules in mineral oil (MO) and trimethylolpropane triester without C=C. However, the lightning impulse breakdown voltage (LI Vb) of trimethylolpropane triester is still significantly lower than that of MO at the large gap. Therefore, the transition from slow to fast streamers under low lighting impulse voltage is determined by the ester group rather than by C=C and β-H. The ester group may attract more electrons, impacting itself more compared to alkane in MO and facilitating the transition from slow to fast streamers.

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Structure, Electronic And Vibrational Study of 7-Methyl-2,3-Dihydro-(1,3)Thiazolo(3,2-A) Pyrimidin-5-One by Using Density Functional Theory

Journal of Institute of Science and Technology ◽

10.3126/jist.v22i2.19589 ◽

2018 ◽

Vol 22 (2) ◽

pp. 1-11

Author(s):

Bhawani Datt Joshi ◽

Janga Bahadur Khadka ◽

Atamram Bhatt

Keyword(s):

Density Functional Theory ◽

Molecular Orbital ◽

Density Functional ◽

Basis Set ◽

Orbital Energy ◽

Potential Energy Distribution ◽

Functional Theory ◽

Hartree Fock ◽

Solvent Phase ◽

Lowest Unoccupied Molecular Orbital

We have presented molecular structure and vibrational wavenumber assignments of 7-methyl-2,3-dihydro-(1,3)thiazolo(3,2-a)pyrimidin-5-one. Both ab initio Hartree-Fock and density functional theory employing 6-311++G(d,p) basis set have been used for the calculations. The scaled values of the calculated vibrational frequencies were used for assignments on the basis of potential energy distribution. The structure-activity relation has been interpreted by mapping molecular electrostatic potential surface. Electronic properties have been analyzed by using time dependent density functional theory (TD-DFT) for both gaseous and solvent phase. The calculated HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy values show that the charge transfer occurs within the molecule. Journal of Institute of Science and TechnologyVolume 22, Issue 2, January 2018, Page: 1-11

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Electronic and geometric structure of AuxCuy clusters studied by density functional theory

International Journal of Modern Physics C ◽

10.1142/s0129183114500119 ◽

2014 ◽

Vol 25 (06) ◽

pp. 1450011 ◽

Cited By ~ 4

Author(s):

Y. Kadioglu ◽

O. Üzengi Aktürk ◽

M. Tomak

Keyword(s):

Density Functional Theory ◽

Molecular Orbital ◽

Density Functional ◽

Local Density ◽

Three Dimensional ◽

Binding Energies ◽

Generalized Gradient ◽

Functional Theory ◽

Highest Occupied Molecular Orbital ◽

Lowest Unoccupied Molecular Orbital

We have determined the stable structures of Au Cu n, Au 2 Cu n, Au 3 Cu n and Au x Cu 8-x clusters. It has been observed that Au Cu n, Au 2 Cu n and Au 3 Cu n systems have two-dimensional (2D) structures up to six atoms and they become three-dimensional (3D) afterwards. Au x Cu 8-x clusters favor 3D structures till the Au 7 Cu 1 cluster. We have found a lowest energy isomer of Au 6 Cu 2 from the literature. Bond lengths, binding energies, density of states (DOS), highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) gaps, ionization potential (IP) and electron affinity (EA) have been calculated for these structures using the first principles density functional theory (DFT) within the generalized gradient approximation (GGA) and the local density approximation (LDA). Generally, we have observed the overlap between s electrons of Cu and p electrons of Au near the Fermi level. Charge transfers are calculated by using the Löwdin analysis. It is observed that one Cu atom does not significantly modify the clusters which have more gold atoms. It is also seen that these clusters generally have nonmagnetic properties and results are consistent with the hybridization between s and d orbitals of Au in Au x Cu 8-x clusters.

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Theoretical studies on lindqvist polyoxometalates [M6O19]n−(M = Mo, W, n=2; M = V, Nb, Ta, n=8) and derivatives: Electronic structures, stability and bonding

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633617500547 ◽

2017 ◽

Vol 16 (06) ◽

pp. 1750054 ◽

Cited By ~ 2

Author(s):

Xiao-Fang Su ◽

Bo Zhu ◽

Cai-Xia Wu ◽

Li-Kai Yan ◽

Zhong-Min Su

Keyword(s):

Charge Density ◽

Molecular Orbital ◽

Electronic Structures ◽

Density Functional ◽

Geometrical Structure ◽

Energy Gap ◽

Lumo Energy ◽

Functional Theory ◽

Highest Occupied Molecular Orbital ◽

Lowest Unoccupied Molecular Orbital

The geometrical and electronic structures of [M6O[Formula: see text]][Formula: see text] (M [Formula: see text] Mo, W, [Formula: see text]; M [Formula: see text] V, Nb, Ta, [Formula: see text]) and their derivatives were investigated by using density functional theory methods. The results indicate that the geometrical structure of [V6O[Formula: see text]][Formula: see text] is not different from other Lindqvist-type anions. The energy gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) (HOMO[Formula: see text]LUMO energy gap) of [V6O[Formula: see text]][Formula: see text] is smaller than those of same charge anions, [Nb6O[Formula: see text]][Formula: see text] and [Ta6O[Formula: see text]][Formula: see text]. In addition, the charge density [Formula: see text] of [V6O[Formula: see text]][Formula: see text] is larger when compared with those of other studied clusters. The investigation on the derivatives shows that the valence of V atom (V[Formula: see text] or V[Formula: see text]) and the methoxy ligand influence the HOMO[Formula: see text]LUMO energy gap and the charge density [Formula: see text] of the studied clusters.

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On the Use of DFT+U to Describe the Electronic Structure of TiO2 Nanoparticles: (TiO2)35 as a Case Study

10.26434/chemrxiv.12213536.v1 ◽

2020 ◽

Author(s):

Angel Morales ◽

Stephen Rhatigan ◽

Michael Nolan ◽

Frances Illas

Keyword(s):

Density Functional ◽

Energy Gap ◽

Plane Waves ◽

Basis Set ◽

Basis Sets ◽

Functional Theory ◽

The Density Functional Theory ◽

Structural And Electronic Properties ◽

Rotationally Invariant

One of the main drawbacks in the density functional theory (DFT) formalism is the underestimation of the energy gaps in semiconducting materials. The combination of DFT with an explicit treatment of electronic correlation with a Hubbard-like model, known as DFT+U method, has been extensively applied to open up the energy gap in materials. Here, we introduce a systematic study where the selection of U parameter is analyzed considering two different basis sets: plane-waves (PWs) and numerical atomic orbitals (NAOs), together with different implementations for including U, to investigate the structural and electronic properties of a well-defined bipyramidal (TiO2)35 nanoparticle (NP). This study reveals, as expected, that a certain U value can reproduce the experimental value for the energy gap. However, there is a high dependence on the choice of basis set and, and on the +U parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in FHI-aims, requires a lower U value than the simplified rotationally invariant approaches as implemented in VASP. Therefore, the transferability of U values between codes is unfeasible and not recommended, demanding initial benchmark studies for the property of interest as a reference to determine the appropriate value of U.

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