RHF Methods Research Articles

Ab-initio and density functional theory (DFT) computational study of the effect of fluorine on the electronic, optical, thermodynamic, hole and electron transport properties of the circumanthracene molecule

In this paper, a systematic study of the electronic, optical, thermodynamic, optoelectronic, and nonlinear optical properties with RHF, B3LYP, wB97XD and BPBE methods using the cc-pVDZ basis set have been described to investigate the influence of fluorine (F) atom, which is an electron donor, on the circumanthracene (C40H16). Global reactivity descriptors, hole and electron transport properties were also calculated and compared with other studies on the same molecule. DFT/B3LYP results show that the undoped C40H16 molecule (Egap = 2.135 eV) and its fluorine-doped derivatives (C40F16 and C40H10F6) are semiconducting materials. However, doping the C40H16 molecule with the fluorine atom, partially or totally, favors the creation of a strong donor-acceptor system by considerably reducing its energy gap (Egap). The energy gap values of molecules doped using DFT/B3LYP method are 2.020 eV and 2.081 eV for the C40F16 and C40H10F6 molecules, respectively. These gap energies are below 3 eV, which favours the electronic properties of these molecules. They can be used to design organic solar cells. The nonlinear optical parameters were calculated and compared with those of urea. The values of βmol and μ calculated for C40F16 and C40H10F6 are higher than those of urea; this shows that these two materials have good nonlinear optical properties and therefore, are very good candidates for the design of optoelectronics and photonics devices. Futhermore, our results show that the perfluorination effect on the circumanthracene molecule increases the hole and electron reorganization energies, the vertical and adiabatic electron affinities and ionization energies, the optoelectronic and nonlinear optical properties, the transition excitation energy and the reactivity indices. The reorganization energies values suggest that these materials have promising transport properties. The natural bond orbital (NBO) analysis was also performed to determine the stability energy and charge delocalization in molecules. The theoretical results of the compounds studied in our work are in agreement with the experimental results. This confirms their molecular structures.

Electronic, non-linear optical, optoelectronic, and thermodynamic properties of undoped and doped bis (ethylenedithio) tetraselenafulvalene (BETS) (C10H8S4Se4) molecule: first study using ab initio investigation.

We have performed the ab initio calculation of the undoped and doped molecules bis (ethylenedithio) tetraselenafulvalene (BETS). Carbone (C) atoms have been substituted by Boron (B) to investigate their effects on the electronic structure and nonlinear optical, optoelectronic, and thermodynamic properties of BETS molecule. The RHF and hybrid density functional theories (WB97XD, B3PW91, and B3LYP) methods were applied, using the cc-pVDZ basis set. We found that the energy gap (Egap) of the doped molecules are respectively 2.476eV and 2.569eV for C8B2H8S4Se4 and C7B3H8S4Se4 with B3LYP/cc-pVDZ basis set, lower than one of the undoped molecule (3.316eV). The significant increase values of polarizability (˂α˃) and first order hyperpolarizability (β) of the doped compounds, especially in C8B2H8S4Se4 (< α > = 4.5315 × 10-23 esu, β = 22,672.27 × 10-33 esu and < α > = 4.518 × 10-23 esu, β = 23,657.43 × 10-33 esu respectively for B3LYP and B3PW91) compared to those of the undoped molecule (< α > = 4.3602 × 10-23 esu, β = 1290.38 × 10-33 esu, and < α > = 4.518 × 10-23 esu) show that the new molecules have a good nonlinear optical property. Results suggest that these molecules doped with boron are a potential candidate as semiconductors compounds and nonlinear optical materials.

Polarization switching in nanoscale ferroelectric composites containing PVDF polymer film and graphene layers

Modeling and computer study of a composite nanostructure containing a ferroelectric PVDF polymer and graphene layers were carried out in this work by molecular dynamic simulation and semiempirical quantum PM3 RHF method using the HyperChem software. It is shown here that the inclusion of graphene layers into the PVDF ferroelectric polymer increases the coercive field and decreases the polarization switching time of this composite structure. It is possible due to decrease in the damping coefficient of the Landau-Khalatnikov kinetic equation of the Landau-Ginzburg-Devonshire theory for two-dimensional ferroelectrics. Heterostructures with adjustable polarization switching times can be constructed based on such approach.

Ab initio investigation of nonlinear optical, electronic, and thermodynamic properties of BEDT-TTF molecule: doping with boron

In this study, the RHF, B3LYP and wB97XD methods with cc-pVDZ basis set have been used to investigate the influence of carbon atoms substitution with boron atoms on the non-linear optical, electronic, optoelectronic and thermodynamic properties of BEDT-TTF (C10H8S8). The results show that the undoped molecule denoted BEDT-TTF or ET (Eg = 3.88 eV) and its derivatives are semi-conductors materials. However, doping C10H8S8 with both 3B and 2B, creating a strong donor-acceptor system and considerably improves its energies gap (Egap). The Eg values of these doped molecules are between 2.2 and 2.39 eV less than 3 eV, which makes more interesting electronic properties. The nonlinear optical parameters such as dipole moment (μ), average polarizability ˂α˃ and first-order hyperpolarizability (βmol) have been calculated and compared with the corresponding values of Urea used as prototypical material to study the NLO properties of the compound. These values obtained indicate that these materials exhibit good nonlinear optical properties. Moreover, we have also computed the chemical softness (ς), ionization potential (IP), electron affinity (AE), global hardness (η), refractive index (n), dielectric constant (ε), electric field (E) and electric susceptibility (χ), total electronic energy (Eo), enthalpy H, entropy S. These results indicate that these new materials doped with boron are promising candidates for the construction of optoelectronics and photonic devices.

Effect of metalation on some graphene nanoribbons for potential application as donor in organic photovoltaic cells

The present work is a systematic and theoretical study performed on three organometallic p-conjugated molecules based on graphene nanoribbons (GNRs) to act as potential donor material in organic photovoltaic cells, using the rhf, b3lyp and bpbe methods together with the 6–31 + g(d,p) basis. Analysis is made on HOMO, LUMO, bandgap, reorganization energy, open circuit voltage, the driving force, and nonlinear optical properties. These organic photovoltaic properties are predicted with the aid of PCBM as modelled acceptor. Results reveal positive agreement with traditional classical and experimental organic values, presenting the fact that metalated GNRs may be used as an effective and potential donor of electron in organic Bulk Heterojunction solar cells, owing to its enhanced nonlinear and photovoltaic properties. The values obtained for the reorganization energy, driving force and nonlinear optical properties are promissory properties that may be directly implemented in the investigated photovoltaic material. The power conversion efficiency obtained for Rb-perylene is seen to be around the maximum current value for organic photovoltaic cell. Rb-perylene shows the best organic photovoltaic properties followed by k-azulene then k-phenanthrene. The methodological approach offered in this research might aid in computer assisted-design of OPV materials.

Determination of the structural, electronic, optoelectronic and thermodynamic properties of the methylxanthine molecules theophylline and theobromine.

RHF and DFT (wB97XD and B3LYP) methods with the 6-31++G** basis set have been used to study structural, optoelectronic and thermodynamic properties of Theophylline and Theobromine. Dipole moment, average polarizability, anisotropy, first-order molecular hyperpolarizability, second-order molecular polarizability, HOMO and LOMO energy gap, molar refractivity, chemical hardness, chemical softness, electronic chemical potential, electronegativity, electrophilicity index, dielectric constant, electric susceptibility, refractive index and their thermodynamic properties have equally been calculated. To understand the vibrational analysis of our system, IR and RAMAN frequencies were calculated and described. Results reveal that molecules can have applications in linear and nonlinear optical devices, photonic devices and in molecular electronics. Equally, from dipole moment, average polarizability, anisotropy, first-order molecular hyperpolarizability, second-order molecular polarizability, HOMO and LOMO energy gap, molar refractivity, chemical hardness, chemical softness, electronic chemical potential, electronegativity, electrophilicity index and literature we suggest that Theophylline and Theobromine be consider as candidates for the treatment of COVID-19 and other respiratory diseases.Electronic supplementary materialThe online version of this article (10.1007/s11082-020-02617-w) contains supplementary material, which is available to authorized users.

Theoretical study of optoelectronic properties of the molecule 2-cyano-3-[4-(diphenylamino)phenyl] acrylic acid

2-Cyano-3-[4-(diphenylamino)phenyl]acrylic acid is one of the most important dyes used in DSSC. In this work, the RHF and DFT (B3LYP and WB97XD) methods along with the 6-31+G** have been used to study the structural, optoelectronic and thermodynamic properties of the 2-cyano-3-[4-(diphenylamino)phenyl]acrylic acid. The dipole moment (µ), polarizability (α0), anisotropy of polarizability (Δα), hyperpolarizability (β0), HOMO and LOMO energy, energy gap (Egap), dielectric constant (e), electric susceptibility (χ), refractive index (η) and thermodynamic properties of this molecule have been calculated using the same levels of theory. The entropy and enthalpy have also been calculated. In order to understand the vibrational analysis of our system, the IR and RAMAN frequencies were calculated and described. The dipole moment average polarizability and first-order molecular hyperpolarizability of the studied molecule indicate that the compound is a good candidate as nonlinear optical materials.

Synthesis, Spectrometric Characterization, X-Ray Crystallography and Quantum Chemical Calculations of 2-oxo-2H-chromen-7-yl Propionate

The title compound, (I), has been solved by direct methods and refined to a final R value of 0.038 for 1835 independent reflections. In the structure, the planar [r.m.s deviation = 0.014 Å] chromen-2-one ring and the 7-propionate side chain are inclined to one another at an acute angle of 65.34(9)°. The molecules form R₄⁴ (30) tetrameric units via C—H···O interactions which extend into layers approximately parallel to the <i>ab</i> plane. Furthermore, the crystal structure is supported by π–π stacking interactions between neighbouring benzene and pyrone or coumarin rings [centroid–centroid distances in the range 3.6097(8)–3.6475(9)Å], as well as C–H···π interactions [H···centroid distances in the range 2.95–3.00Å]. The molecular geometry of (I) was also optimized using density functional theory (DFT/RB3LYP), RMP2 and RHF methods with the 6-311⁺⁺G(<i>d</i>, <i>p</i>) basis set in ground state. The theoretical data resulting from these quantum chemical calculations are in good agreement with the observed structure, although the observed C—O—C—C torsion angle between the coumarin ring system and the 7-propionate side chain (121.49 (16)°) is somewhat lower than the DFT/RB3LYP calculated value (132.32°) and larger than the RMP2 (114.65°) and the RHF (69.19°) values. Hirshfeld surface analysis has been used to confirm and quantify the supramolecular interactions.

Ab Initio Study on Electronic Structure of Some Imidazole Derivatives and Its Correlation with Corrosion Inhibition Properties

Imidazole and some of its derivatives have been known as a good candidate for corrosion inhibition application. In this study, ab initio calculation was carried out for several imidazole derivatives i.e. 2-phenylimidazole[1,2-α]pyridine, 6-methyl-2-phenylimidazole[1,2-α]pyridine, 6-methyl-2-(4-metoxyplenylimidazole)[1,2-α]pyridine, and 6-methyl-2-(4-chlorophenylimidazole)[1,2α]pyridine, in order to investigate their electronic properties as well as its correlation with their corrosion inhibition properties. Calculations were performed using Firefly software package with RHF method and 6-31G(d,p) basis set. Based on calculation results and analysis, it was found that 6-methyl-2-(4-metoxyphenylimidazole) [1,2α]pyridine compound has better potential as corrosion inhibitor than the rest of the compounds due to its small HOMO-LUMO energy gap, low ionization potential, low electron affinity, low electronegativity, and low global hardness i.e. 10.184 eV, 7.199 eV, -2.985 eV, 2.107 eV and 5.092 eV respectively. This compound also has the highest global softness (0.098 eV), while the greatest value of the dipole moment was owned by 6-methyl-2-(4-chlorophenylimidazole)[1,2α]pyridine with value of 6.125 Debye due to the existence of Cl atom that has larger polarity than the other substituents.

Study of some properties of quinone derivatives from quantum chemical calculations

The electronic energies, electronic structures and the linear and non linear optical properties of some Quinone derivative have been calculated by adopting the LDA and GGA approximations for the exchange–correlation potential within the MP2 and DFT methods. These properties were equally determined using the RHF method. The calculated electronic structures show that the molecules have energy band gaps (Eg) less than 2 eV. The work functions and some optical constants such as the refractive index, reflectivity, electrical susceptibility, optical conductivity, thermal conductivity, dipole moment, average polarizability and hyperpolarizability have been calculated. The dielectric constants, ionization potentials, electron affinities, electronegativities, hardness and total electronic energies have also been calculated. Most of the results show that the molecules could have potential applications as semiconductor components, nonlinear optical materials, and possible building materials for molecular electronics and photonic devices.

The Creation of C13H20BeLi2SeSi. The Proposal of a Bio- Inorganic Molecule, Using Ab Initio Methods for The Genesis of a Nano Membrane

The work is an evolution of research already begin and in development. Therefore, we can observe a part that has already been commented that presents the whole development of the research from its beginning. Preliminary bibliographic studies did not reveal any works with characteristics studied here. With this arrangement of atoms and employees with such goals. Going beyond with imagination using quantum chemistry in calculations to obtain probable one new bio-inorganic molecule, to the Genesis of a bioinorganic membrane with a combination of the elements Be, Li, Se, Si, C and H. After calculation a bio-inorganic seed molecule from the previous combination, it led to the search for a molecule that could carry the structure of a membrane. From simple molecular dynamics, through classical calculations, the structure of the molecule was stabilized. An advanced study of quantum chemistry using ab initio, HF (Hartree-Fock) method in various basis is applied and the expectation of the stabilization of the Genesis of this bio-inorganic was promising. The calculations made so far admit a seed molecule at this stage of the quantum calculations of the arrangement of the elements we have chosen, obtaining a highly reactive molecule with the shape polar-apolar-polar. Calculations obtained in the ab initio RHF method, on the set of bases used, indicate that the simulated molecule, C13H20BeLi2 SeSi, is acceptable by quantum chemistry. Its structure has polarity at its ends, having the characteristic polar-apolar-polar. Even using a simple base set the polar-apolar-polar characteristic is predominant. The set of bases used that have the best compatible, more precise results are CC-pVTZ and 6-311G (3df, 3pd). In the CC-pVTZ base set, the charge density in relation to 6-311G (3df, 3pd) is 50% lower. The structure of the bio-inorganic seed molecule for a bio-membrane genesis that challenge the current concepts of a protective mantle structure of a cell such as bio-membrane to date is promising, challenging. Leaving to the biochemists their experimental synthesis.

Electronic structure, physico-chemical, linear and non linear optical properties analysis of coronene, 6B-, 6N-, 3B3N- substituted C24H12 using RHF, B3LYP and wB97XD methods

In this work we have investigated the effects of substituting carbon atoms with B, N and BN on the electronic structure, physico-chemical, linear and non linear optical properties of Coronene (C24H12) using HF and DFT methods. We have calculated total electronic energy E0, zero point vibrational energy ZPVE, the enthalpy H, entropy S, molar heat capacity at constant volume Cv, ionization potential IP, electron affinity EA, hardness $$\kappa$$ , softness $$\vartheta$$ , electronegativity EN, dipole moment µ, average polarizability $$ $$ , anisotropy $$\Delta \alpha$$ , the first molecular hyperpolarizability βmol, second order hyperpolarizability $$\gamma_{av}$$ , HOMO–LUMO Energy gap Egap, work function EF, refractive index n, susceptibility χ, dielectric constant e and molar refractivity MR of coronene (C24H12), the 6B-, 6N- and 3B3N- substitute-doped C24H12 C18B6H12 C18N6H12 and C18B3N3H12. The Egap values of the molecules are between 0.91 and 2.36 eV. We observed that βmol changes slightly when C24H12 is doped with either 6B or 6N even though their βmol values are too small. However, by doping C24H12 with both 3B and 3N, creating a strong donor–acceptor system, a very large increase in µ and βmol was found for C18B3N3H12. This study was done using RHF, B3LYP and wB97XD methods with the cc-pVDZ basis set. The studies have shown that doping decreases some of the above properties significantly while some increases significantly compared to pure coronene, suggesting that 6B-, 6N-, and 3B3N-doped Coronene as serious candidates for electronics, optoelectronics and photonic devices.

Theoretical study of optoelectronic and thermodynamic properties of molecule 4-[2-(2-N,N-dihydroxy amino thiophene)vinyl]benzanamine: Influence of hydroxyl position

In this work we have theoretically determined the optoelectronic and thermodynamic properties of the donor-acceptor molecule 4-[2-(2-N,N-dihydroxy amino thiophene)vinyl]benzanamine and study the influence of the position of the hydroxyl group on some of the optoelectronic properties. The results obtained from the B3LYP, B3PW91 and RHF methods by employing the 6−311++G∗∗ basis set show that 4-[2-(2-N,N-dihydroxy amino thiophene)vinyl]benzanamine and N,N-dihydroxy-4[2-(2-amino thiophene)vinyl]benzanamine are semiconductor materials with good optoelectronic properties and may have applications in thin films, photonics, electronics, optoelectronics, etc. We also observed that the position of the hydroxyl group in the molecules influences their optoelectronic and thermodynamic properties.

Estimating the activation energy of the displacement of Mg atoms in the channels of B25C4Mg1.42 crystals

The activation energy of displacement of Mg atoms through channels of B25C4Mg1.42 crystals is estimated using quantum chemical calculations (DFT (B3LYP potential), RHF, and UHF methods, 3-21G basis set) of the element of the structure modeling the channel and location of Mg atoms in it. The changes in the activation energy at the replacement of Mg atoms by Na and Li atoms were estimated. The greatest decreasing in the activation energy was detected for Li atoms. The obtained results can be regarded as a theoretical background for development of conducting systems based on B25C4Mg1.42 crystals.

Quantum chemical evaluation of the corrosion inhibition of novel aromatic hydrazide derivatives on mild steel in hydrochloric acid

The theoretical evaluations of the corrosion inhibition efficiency of 2-(3,4,5-tri-R-benzylidene) hydrazinecarbothioamide, (R=H, CH3, OCH3 and NH2), were done using RHF and DFT-B3LYP methods with 6-31G(d) basis set in gas phase, aqueous and acidic solutions. The correlation between the molecular structures of these compounds and their theoretically predicted inhibition effects was obtained from the quantum chemical evaluations, such that the structural parameters provided insights into the possible inhibition mechanism. 2-(3,4,5-triaminebenzylidene) hydrazinecarbothioamide showed a larger tendency of adsorption through chemisorption and physisorption and thus was identified to be the best potential candidate for excellent corrosion inhibition among the studied compounds.

The Pyranoside-into-Furanoside Rearrangement of Alkyl Glycosides: Scope and Limitations

The pyranoside-into-furanoside (PIF) rearrangement was recently reported as a useful tool for the synthesis of furanoside-containing complex oligosaccharides. Until now, this transformation has only been described for some protected allyl-β- d -galactosides and one l -fucoside. In this communication its applicability is expanded. The formation of furanosides was observed under acid-promoted sulfation for a series of galactosides with varying alkyl substituents at the anomeric position as well as for several fucosides and glucosides. Meanwhile, furanoside formation was not detected in the case of mannopyranosides. The different reactivity of substrates was explained by values of activation barriers of endocyclic C1–O5 bond cleavage calculated by ab initio RHF methods. The reported results clarify the scope and limitations of the PIF rearrangement, which is important for its application in the synthesis of carbohydrate structures of practical meaning.

Vibrational, NMR and UV–Visible spectroscopic investigation, VCD and NLO studies on Benzophenone thiosemicarbazone using computational calculations

In order to explore the unbelievable NLO property of prepared Benzophenone thiosemicarbazone (BPTSC), the experimental and theoretical investigation has been made. The theoretical calculations were made using RHF and CAM-B3LYP methods at 6-311++G(d,p) basis set. The title compound contains CS ligand which helps to improve the second harmonic generation (SHG) efficiency. The molecule has been examined in terms of the vibrational, electronic and optical properties. The entire molecular behavior was studied by their fundamental IR and Raman wavenumbers and was compared with the theoretical aspect. The molecular chirality has been studied by performing vibrational circular dichroism (circularly polarized infrared radiation). The Mulliken charge levels of the compound ensure the perturbation of atomic charges according to the ligand. The molecular interaction of frontier orbitals emphasizes the modification of chemical properties of the compound through the reaction path. The enormous amount of NLO activity was induced by the Benzophenone in thiosemicarbazone. The Gibbs free energy was evaluated at different temperature and from which the enhancement of chemical stability was stressed. The VCD spectrum was simulated and the optical dichroism of the compound has been analyzed.

A comparative study of novel chalcone derivative by X-ray and quantum chemical calculations (Ab-initio and DFT): Experimental and theoretical approach

ABSTRACTA novel bio-organic molecule, 3-(3-chloro-4-methoxy-phenyl)-1-(4,5-dimethoxy-2-methyl phenyl) prop-2-en-1-one (I), has been synthesized and characterized by FTIR, 1H, and 13C NMR. To understand the role of solvents, UV-vis absorption, and fluorescence study has been carried out using different solvents. The single-crystal X-ray diffraction technique has been studied to confirm the three dimensional structure of the compound and the hydrogen bond interactions involved in the stability of the structure. The ab-initio and density functional theory (DFT) are used to optimize the molecular structure. The calculated results show that the predicted geometry can well reproduce structural parameters. In addition, frontier molecular orbitals and Mullikan charge distributions are carried out by using RHF and B3LYP methods. The synthesized compound has been screened for its antimicrobial and antifungal activities against different panel of organisms.

Molecular structure and spectroscopic characterization of Carbamazepine with experimental techniques and DFT quantum chemical calculations

A systematic vibrational spectroscopic assignment and analysis of Carbamazepine has been carried out by using FT-IR, FT-Raman and UV spectral data. The vibrational analysis were aided by electronic structure calculations – ab initio (RHF) and hybrid density functional methods (B3LYP) performed with standard basis set 6-31G(d,p). Molecular equilibrium geometries, electronic energies, natural bond order analysis, harmonic vibrational frequencies and IR intensities have been computed. A detailed interpretation of the vibrational spectra of the molecule has been made on the basis of the calculated Potential Energy Distribution (PED) by VEDA program. UV–visible spectrum of the compound was also recorded and the electronic properties, such as HOMO and LUMO energies and λmax were determined by HF/6-311++G(d,p) Time-Dependent method. The thermodynamic functions of the title molecule were also performed using the RHF and DFT methods. The restricted Hartree–Fock and density functional theory-based nuclear magnetic resonance (NMR) calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of Carbamazepine.

Restricted Hartree Fock using complex-valued orbitals: a long-known but neglected tool in electronic structure theory.

Restricted Hartree Fock using complex-valued orbitals (cRHF) is studied. We introduce an orbital pairing theorem, with which we obtain a concise connection between cRHF and real-valued RHF, and use it to uncover the close relationship between cRHF, unrestricted Hartree Fock, and generalized valence bond perfect pairing. This enables an intuition for cRHF, contrasting with the generally unintuitive nature of complex orbitals. We also describe an efficient computer implementation of cRHF and its corresponding stability analysis. By applying cRHF to the Be + H2 insertion reaction, a Woodward-Hoffmann violating reaction, and a symmetry-driven conical intersection, we demonstrate in genuine molecular systems that cRHF is capable of removing certain potential energy surface singularities that plague real-valued RHF and related methods. This complements earlier work that showed this capability in a model system. We also describe how cRHF is the preferred RHF method for certain radicaloid systems like singlet oxygen and antiaromatic molecules. For singlet O2, we show that standard methods fail even at the equilibrium geometry. An implication of this work is that, regardless of their individual efficacies, cRHF solutions to the HF equations are fairly commonplace.