Becke-Lee-Yang-Parr Research Articles

Anisotropic structure and dynamics of the solvation shell of a benzene solute in liquid water from ab initio molecular dynamics simulations.

The anisotropic structure and dynamics of the hydration shell of a benzene solute in liquid water have been investigated by means of ab initio molecular dynamics simulations using the BLYP (Becke-Lee-Yang-Parr) and dispersion corrected BLYP-D functionals. The main focus has been to look at the influence of π-hydrogen-bonding and hydrophobic interactions on the distance and angle resolved various structural and dynamic properties of solvation shell. The structure of hydration shell water molecules around benzene is found to be highly anisotropic as revealed by the radial distribution functions of different conical regions and joint radial/angular distribution functions. The benzene-water dimer potential energy curves are calculated for a variety of orientations of water along the axial and equatorial directions for both BLYP and BLYP-D functionals. The simulation results of the hydration shell structure of benzene, particularly the axial and equatorial benzene-water RDFs are discussed based on the differences in the benzene-water potential energies for different orientations and functionals. The inter-particle distance/angle correlations show an enhanced water structure in the solvation shell of benzene compared to that between the solvation shell and bulk and also between the bulk molecules. On average, a single πH-bond is found to be formed between water and benzene in the 45° axial conical region of the solvation shell. The πH-bonded water molecules are found to have faster translational dynamics and also found to follow a fast jump mechanism of reorientation to change their hydrogen bonded partners. The presence of π-hydrogen-bonded water makes the overall dynamics of the axial region faster than that of the equatorial region where the water molecules are hydrophobically solvated and hydrogen bonded to other water molecules.

Density functional theory studies of conformational stabilities and rotational barriers of 2- and 3-thiophenecarboxaldehydes

The molecular structures, conformational stabilities, and infrared vibrational wavenumbers of 2-thiophenecarboxaldehyde and 3-thiophenecarboxaldehyde are computed using Becke-3—Lee—Yang—Parr (B3LYP) with the 6-311++G** basis set. From the computations, cis-2-thiophenecarboxaldehyde is found to be more stable than the transfer conformer with an energy difference of 1.22 kcal/mol, while trans-3-thiophenecarboxaldehyde is found to be more stable than the cis conformer by 0.89 kcal/mol. The computed dipole moments, structural parameters, relative stabilities of the conformers and infrared vibrational wavenumbers of the two molecules coherently support the experimental data in the literature. The normal vibrational wavenumbers are characterized in terms of the potential energy distribution using the VEDA4 program. The effect of solvents on the conformational stability of the molecules in nine different solvents is investigated using the polarizable continuum model.

Structure analysis and spectroscopic characterization of 2-Fluoro-3-Methylpyridine-5-Boronic Acid with experimental (FT-IR, Raman, NMR and XRD) techniques and quantum chemical calculations

Possible stable conformers, geometrical molecular structures, vibrational properties as well as band assignments, nuclear magnetic shielding tensors of 2-Fluoro-3-Methylpyridine-5-Boronic Acid (2F3MP5BA) were studied experimentally and theoretically using FT-IR, Raman, (CP/MAS) NMR and XRD spectroscopic methods. FT-IR and Raman spectra were evaluated in the region of 3500–400 cm−1, and 3200–400 cm−1, respectively. The optimized geometric structures, vibrational wavenumbers and nuclear magnetic shielding tensors were examined using Becke-3–Lee–Yang–Parr (B3LYP) hybrid density functional theory method with 6–311++G(d, p) basis set. 1H, 13C NMR chemical shifts were calculated using the gauge invariant atomic orbital (GIAO) method. 1H, 13C, APT and HETCOR NMR experiments of title molecule were carried out in DMSO solution. 13C CP/MAS NMR measurement was done with 4 mm zirconium rotor and glycine was used as an external standard. Single crystal of 2F3MP5BA was also prepared for XRD measurements. Assignments of vibrational wavenumbers were also strengthened by calculating the total energy distribution (TED) values using scaled quantum mechanical (SQM) method.

Halogen and solvent effects on the conformational, vibrational and electronic properties of 1,4-diformylpiperazine: A combined experimental and DFT study

The molecular structure and properties of 1,4-diformylpiperazine (1,4-dfp, C6H[Formula: see text]N2O2) were investigated by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and density functional theory (DFT). The Becke-3-Lee–Yang–Parr (B3LYP) functional was used with the 6-31[Formula: see text]G(d,p) basis set. Total energy distribution (TED) analysis of normal modes was performed to identify characteristic frequencies by the scaled quantum mechanical (SQM) method. Halogeno-analogs of 1,4-dfp were studied to understand the halogen effect. Computations were focused on five conformational isomers of the compounds in the gas phase and in solutions. The computed and experimental frequencies of the C[Formula: see text]O stretching vibration of 1,4-dfp were correlated with the empirical solvent parameters such as the Kirkwood–Bauer–Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSER). The electronic properties of the compounds were also examined. The findings from the present work may be useful to understand systems involving the halogens and conformational changes analogous to the compounds investigated.

Multiple approach to model unpaired spin density effects in H-ZSM5 zeolite with extra-framework O atom: H-abstraction reaction from methane

The interaction of methane with an extra-framework oxygen atom in acidic zeolite (H-ZSM5) porous substrate has been investigated by means of different state of the art calculations using two model systems in their triplet spin state: zeolite was modelled both by its crystallographic structure subject to periodic boundary condition and by cluster approach in gas-phase. We have evaluated the energetics of H-abstraction reaction from methane within the (010) straight channel of acidic zeolite by different computational approaches. First by in bulk plane waves Density Functional Theory (with and without dispersion energy correction) and then, in gas-phase cluster, by typical quantum chemistry approaches based on molecular orbital theory, where electronic wave function is expanded in Gaussian basis sets, within variational or perturbative schemes. Reaction paths have been determined either by Climbing Image Nudged Elastic Band method (c-NEB) in bulk or by Intrinsic Reaction Coordinate (IRC) method in gas phase. Transition State has been characterized in cluster models using Becke-3-Lee Yang Parr (B3LYP) and BeckeHalf&HalfLeeYangParr (BHLYP) hybrid functionals. Calculated energy barriers and all results allow an interesting vis-à-vis of commonly used, alternative, often exclusive models. This study indicates that open shell systems composed of O atoms and H-ZSM5 are worth to be considered in H-abstraction from small hydrocarbons in applicative processes.

Structural characterization, solvent effects on nuclear magnetic shielding tensors, experimental and theoretical DFT studies on the vibrational and NMR spectra of 3-(acrylamido)phenylboronic acid

Structural elucidation of 3-(acrylamido)phenylboronic acid (C9H10BNO3) was carried out with 1H, 13C and HETCOR NMR techniques. Solvent effects on nuclear magnetic shielding tensors were examined with deuterated dimethyl sulfoxide, acetone, methanol and water solvents. The correct order of appearance of carbon and hydrogen atoms on NMR scale from highest magnetic field region to the lowest one were investigated using different types of theoretical levels and the details of the levels were presented in this study. Stable structural conformers and vibrational band analysis of the title molecule (C9H10BNO3) were studied both experimental and theoretical viewpoints using FT-IR, Raman spectroscopic methods and density functional theory (DFT). FT-IR and Raman spectra were obtained in the region of 4000–400 cm−1, and 3700–10 cm−1, respectively. Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-31++G(d, p) basis set was included in the search for optimized structures and vibrational wavenumbers. Experimental and theoretical results show that after application of a suitable scaling factor density functional B3LYP method resulted in acceptable results for predicting vibrational wavenumbers except OH and NH stretching modes which is most likely arising from increasing unharmonicity in the high wave number region and possible intra and inter molecular interaction at OH edges those of which are not fully taken into consideration in theoretical processes. To make a more quantitative vibrational assignments, potential energy distribution (PED) values were calculated using VEDA 4 (Vibrational Energy Distribution Analysis) program.

Radical scavenging activity characterization of synthetic isochroman-derivatives of hydroxytyrosol: A gas-phase DFT approach

Hydroxytyrosol (HT) and a set of synthetic isochroman derivatives of HT have been studied with regards to their radical scavenging activity in the gas employing density functional theory (DFT) and the Becke's 3 Lee Yang Parr (B3LYP) functional. Values of molecular descriptors (bond dissociation enthalpy, BDE; ionization potential, IP; proton dissociation enthalpy, PDE; proton affinity, PA; electron transfer energy, ETE; electron accepting power, ɷ+; electron donating power, ɷ−; net electrophilicity, Δɷ±) characterizing the hydrogen atom or electron donating efficiency of test compounds were used. Published experimental findings for the radical scavenging activity of the same compounds using methods such as Rancimat, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation and oxygen radical absorbance capacity were discussed. All the synthetic isochromans were predicted to be more potent hydrogen atom and electron donors than HT, though polarity may affect their performance in lipidic systems. Present findings point out that HT and examined isochromans prefer to scavenge free radicals via hydrogen atom transfer instead of electron donation and that allylic hydrogen atoms are expected to account for a higher activity in comparison to other phenolic antioxidants. The most potent hydrogen atom donor was the one bearing two catechol groups which can form stepwise a di-quinone and then scavenge additional radicals via allylic hydrogen atom donation and subsequent adduct formation. The total enthalpy required for all hydrogen atoms donated by test compounds was the most appropriate index of experimental activity prediction instead of common descriptors.

NMR, FT-IR, Raman and UV–Vis spectroscopic investigation and DFT study of 6-Bromo-3-Pyridinyl Boronic Acid

Possible stable conformers and geometrical molecular structures of 6-Bromo-3-Pyridinyl Boronic acid (6B3PBA; C5H5BBrNO2) were studied experimentally and theoretically using FT-IR and Raman spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–400 cm−1 and 3700–400 cm−1, respectively. The structural properties were investigated further, using 1H, 13C, 1H coupled 13C, HETCOR, COSY and APT NMR techniques. The optimized geometric structures were searched by Becke-3–Lee–Yang–Parr (B3LYP) hybrid density functional theory method with 6-311++G(d, p) basis set. Vibrational wavenumbers of 6B3PBA were calculated whereby B3LYP density functional methods including 6-311++G(d, p), 6-311G(d, p), 6-311G(d), 6-31G(d, p) and 6-31G(d) basis sets. The comparison of the experimentally and theoretically obtained results using mean absolute error and experimental versus calculated correlation coefficients for the vibrational wavenumbers indicates that B3LYP method with 6-311++G(d, p) gives more satisfactory results for predicting vibrational wavenumbers when compared to the 6-311G(d, p), 6-311G(d), 6-31G(d, p) and 6-31G(d) basis sets. However, this method and none of the mentioned methods here seem suitable for the calculations of OH stretching modes, most likely because increasing unharmonicity in the high wave number region and possible intra and inter molecular interactions at OH edges lead some deviations between experimental and theoretical results. Moreover, reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated using scaled quantum mechanical (SQM) method.

Novel Cyanide-Bridged Heterometallic Two-Dimensional Complex of 3-Methylpyridazine: Synthesis, Crystallographical, Vibrational, Thermal and DFT Studies

A novel Cu/Pd heterometallic cyanide-bridged complex of 3-methylpyridazine (3-mpdz), [Cu(3-mpdz)2Pd(µ-CN)4]n, was synthesized and its structure was characterized by FT-IR, Raman, single-crystal X-ray diffraction and thermal/elemental analysis techniques. The conformers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the complex were examined by means of the density functional theory method, the Becke-3–Lee–Yang–Parr (B3LYP) functional and the LANL2DZ basis set. Reliable vibrational assignments were investigated by the potential energy distribution analysis. The complex crystallizes in the triclinic space group P-1 with the unit cell parameters a = 6.6836(4) A, b = 7.7777(5) A, c = 8.9009(6) A, α = 113.573(5)°, β = 94.565(6)° and γ = 92.437(5)°. There is a good interplay between experimental and theoretical findings to understand the complex at molecular level. The synthesised complex with potential industrial applications will add to the literature of the cyanide-bridged tetracyanometallates.

Crystallographic, vibrational and DFT studies of 1-(2-hydroxy-4,5-dimethylphenyl)ethanone

Molecular structure and properties of 1-(2-hydroxy-4,5-dimethylphenyl)ethanone were experimentally investigated by X-ray diffraction technique and vibrational spectroscopy. Experimental results on the molecular structure of the reported compound were supported with computational studies using the density functional theory (DFT), with the Becke-3-Lee–Yang–Parr (B3LYP) functional and the 6-311+G(3df,p) basis set. Potential energy distribution (PED) and potential energy surface (PES) analyses were performed to identify characteristic frequencies and reliable conformational analysis correspondingly. The compound crystallizes in monoclinic space group C2/c with the CO up–OH down conformation. There is a good agreement between the experimentally determined geometrical parameters and vibrational frequencies of the compound to those predicted theoretically.

Synthesis, spectral analysis (FT-IR, 1H NMR, 13C NMR and UV–visible) and quantum chemical studies on molecular geometry, NBO, NLO, chemical reactivity and thermodynamic properties of novel 2-amino-4-(4-(dimethylamino)phenyl)-5-oxo-6-phenyl-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carbonitrile

In the present study novel 2-amino-4-(4-(dimethylamino)phenyl)-5-oxo-6-phenyl-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carbonitrile was synthesized and characterized by FT-IR, 1H NMR, 13C NMR, UV–visible spectroscopy and mass spectral analysis. The chemical calculations were done by DFT level of theory using Becke3–Lee–Yang–Parr (B3LYP) and Coulomb Attenuating Method (CAM-B3LYP)/6-31G(d,p) basis set. 1H, 13C chemical shifts and vibrational wavenumbers were calculated and good correlation with the experimental data has been accomplished. UV–Visible spectrum of the molecule was recorded in the region 200–500nm and the electronic properties and composition were obtained using Time Dependent Density Functional Theory (TDDFT) method. Hyperconjugative interactions were studied with the help of natural bond orbital analysis. Electric dipole moment, polarizability and first static hyperpolarizability values have been calculated. The results show that the title compound possesses nonlinear optical behavior with non-zero values. The thermodynamic properties of the compound were calculated at different temperatures. The local reactivity descriptors show that C(7) is most reactive site for nucleophilic attack.

Trans-dichlorotetrakis(1H-pyrazole-κN2)copper(II): Synthesis, crystal structure, hydrogen bonding graph-sets, vibrational and DFT studies

The copper complex [Cu(HPrz)4]Cl2 (HPrz=Pyrazole) was synthesized and its structure was characterized by FT-IR, Raman and single-crystal X-ray diffraction (XRD) techniques. The structural conformers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the compound were examined by means of the density functional theory (DFT) method, the Becke-3-Lee–Yang–Parr (B3LYP) functional, the 6-311+G(3df,p) and lanl2dz basis sets. Reliable vibrational assignments were investigated by the potential energy distribution (PED) analysis. The compound crystallizes in the monoclinic space group C2/c with the unit cell parameters a=13.5430 (10) Å, b=9.1480 (10) Å, c=14.6480 (10) Å and β=116.7° (5). There is a good agreement between the theoretically predicted structural parameters and vibrational frequencies and those obtained experimentally. The findings of this work reveals further insight into molecular copper(II) pyrazole systems.

Synthesis, characterization, and dielectric properties of polymers functionalized with coumarone and diethanolamine

ABSTRACTA series polymers of the poly(4‐{[bis(2‐hydroxyethyl)amino]methyl}‐2‐oxo‐2H‐chromen‐7‐yl‐2‐methylpropanoate), P(CIMMAOC)‐DEA, were synthesized by modification of poly(4‐(chloromethyl)‐2‐oxo‐2H‐chromen‐7‐yl‐2‐ethylpropanoate), P(CIMMAOC), with diethanolamine (DEA). All polymers were structurally characterized by FTIR, 1H NMR, UV–vis, and Fluorescence spectra. The electronic features of the polymer, such as lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energies and electrostatic potential (ESP), and the vibrational frequencies were computed by the Becke3–Lee–Yang–Parr (B3LYP) functional using 3–21G* basis set. Dielectric measurements for P(CIMMAOC) and P(CIMMAOC)‐DEA were performed by means of an impedance analyzer as a function of frequency and temperature. It was found that the dielectric constant values decreased in the applied frequency range. The values of dielectric constant increased with a rise in concentrations of DEA in polymer for all temperatures. Dielectric constants of P(CIMMAOC) and P(CIMMAOC)‐DEA (60%) were calculated as 3.93 and 12.29 at 1 kHz, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42164.

3-Iodobenzaldehyde: XRD, FT-IR, Raman and DFT studies

The structure of 3-iodobenzaldehyde (3IB) was characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The conformational isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 3IB were examined using density functional theory (DFT) method, with the Becke-3-Lee–Yang–Parr (B3LYP) functional and the 6-311+G(3df,p) basis set for all atoms except for iodine. The LANL2DZ effective core basis set was used for iodine. Potential energy distribution (PED) analysis of normal modes was performed to identify characteristic frequencies. 3IB crystallizes in monoclinic space group P21/c with the O-trans form. There is a good agreement between the theoretically predicted structural parameters, and vibrational frequencies and those obtained experimentally. In order to understand halogen effect, 3-halogenobenzaldehyde [XC6H4CHO; X=F, Cl and Br] was also studied theoretically. The free energy difference between the isomers is small but the rotational barrier is about 8kcal/mol. An atypical behavior of fluorine affecting conformational preference is observed.

Benchmarking quantum mechanical calculations with experimental NMR chemical shifts of 2-HADNT

In this study, both GIAO-DFT and GIAO-MP2 calculations of nuclear magnetic resonance (NMR) spectra were benchmarked with experimental chemical shifts. The experimental chemical shifts were determined experimentally for carbon-13 (C-13) of seven carbon atoms for the TNT degradation product 2-hydroxylamino-4,6-dinitrotoluene (2-HADNT). Quantum mechanics GIAO calculations were implemented using Becke-3-Lee–Yang–Parr (B3LYP) and other six hybrid DFT methods (Becke-1-Lee–Yang–Parr (B1LYP), Becke-half-and-half-Lee–Yang–Parr (BH and HLYP), Cohen–Handy-3-Lee–Yang–Parr (O3LYP), Coulomb-attenuating-B3LYP (CAM-B3LYP), modified-Perdew–Wang-91-Lee–Yang–Parr (mPW1LYP), and Xu-3-Lee–Yang–Parr (X3LYP)) which use the same correlation functional LYP. Calculation results showed that the GIAO-MP2 method gives the most accurate chemical shift values, and O3LYP method provides the best prediction of chemical shifts among the B3LYP and other five DFT methods. Three types of atomic partial charges, Mulliken (MK), electrostatic potential (ESP), and natural bond orbital (NBO), were also calculated using MP2/aug-cc-pVDZ method. A reasonable correlation was discovered between NBO partial charges and experimental chemical shifts of carbon-13 (C-13).

An analysis of hydrated proton diffusion in ab initio molecular dynamics

A detailed understanding of the inherently multiscale proton transport process raises a number of scientifically challenging questions. For example, there remain many (partially addressed) questions on the molecular mechanism for long-range proton migration and the potential for the formation of long-lived traps giving rise to burst-and-rest proton dynamics. Using results from a sizeable collection of ab initio molecular dynamics (AIMD) simulations (totaling ∼2.7 ns) with various density functional approximations (Becke-Lee-Yang-Parr (BLYP), BLYP-D3, Hamprecht-Cohen-Tozer-Handy, B3LYP) and temperatures (300-330 K), equilibrium and dynamical properties of one excess proton and 128 water molecules are studied. Two features in particular (concerted hops and weak hydrogen-bond donors) are investigated to identify modes in the system that are strongly correlated with the onset of periods of burst-and-rest dynamics. The question of concerted hops seeks to identify those time scales over which long-range proton transport can be classified as a series of sequential water hopping events or as a near-simultaneous concerted process along compressed water wires. The coupling of the observed burst-and-rest dynamics with motions of a fourth neighboring water molecule (a weak hydrogen-bond donor) solvating the protonated water molecule is also investigated. The presence (absence) of hydrogen bonds involving this fourth water molecule before and after successful proton hopping events is found to be strongly correlated with periods of burst (rest) dynamics (and consistent with pre-solvation concepts). By analyzing several realizations of the AIMD trajectories on the 100-ps time scale, convergence of statistics can be assessed. For instance, it was observed that the probability for a fourth water molecule to approach the hydronium, if not already proximal at the beginning of the lifetime of the hydronium, is very low, indicative of the formation of stable void regions. Furthermore, the correlations of the neighboring water atoms are identified as the fourth water approaches the hydronium. Finally, the temperature effects on structural and dynamical properties are studied.

Effect of Molecular Interactions and Homologue Number on UV Absorption Spectra of Liquid Crystalline Alkyl Cyanobiphenyl Dimers: DFT Calculations

The ultraviolet (UV) absorption spectra of the liquid crystalline dimer complexes of 4′-n-alkyl-4-cyanobiphenyls (nCB: n = 3, 4, 5 where n is the number of carbon atoms in the alkyl chain) have been presented. The nCB structures have been optimized using the density functional Becke3-Lee-Yang-Parr (B3LYP) hybrid functional with 6-31+G (d) basis set using the crystallographic geometry as input. The electronic structures of the dimer molecules have been computed using the optimized geometries. The spectra of the dimer molecules have been calculated by employing the density functional theory (DFT). The features of electronic transitions and excited states have been calculated via configuration interaction singles (CIS) with the semiempirical Hamiltonian Zerner intermediate neglect of differential overlap (ZINDO). The various modes of molecular interactions and the homologue number are found to be structural parameters affecting the formation of mesophases, UV absorption spectral characteristics, and photo stability of the compounds. These results offer a hint for the calculations involving the different modes of molecular interactions, and separations between dimers, to model photo stability or in tuning the absorbing chromophore to match the wavelength of desired application.

Study On The Structures And Interactions Binary System Composed By The Ionic Liquids [Bmim][Ala] and Water /Methanol Using The Vibrational Spectra

The molecular geometry and vibrational frequencies of the Amino acid ILs 1-butyl-3-methylimidazolium α-aminopropionic acid salt ([bmim][Ala]), [bmim][Ala] and water /Methanol were investigated by the density functional theory (DFT) at the hybrid Becke 3-Lee-Yang-Parr (B3LYP)/6-311++G** level. Attenuated total reflectionFourier transform infrared spectroscopy (ATR-FTIR) of the [bmim][Ala], [bmim][Ala] and water /Methanol have been recorded at different concentrations. The observed vibrational spectra have been resolved and assigned in detail by comparison to the calculated results. The results indicate that the vibrational frequencies obtained by DFT (B3LYP) are in good agreement with the experiment results. The forms and the effect of the hydrogen bond that exist between [bmim][Ala] and water/Methanol have been investigated from the point view of the interaction.

Oxidovanadium(IV) complexes involving dehydroacetic acid and β-diketones of bioinorganic and medicinal relevance: Their synthesis, characterization, thermal behavior and DFT aspects

Six new mixed-ligand complexes of oxidovanadium(IV) of the general composition [VO(dha)(L)(H2O)], where dhaH=dehydroacetic acid, LH=β-diketones, viz., acetoacetanilide (aaaH), o-acetoacetotoluidide (o-aatdH), o-acetoacetanisidide (o-aansH), acetylacetone (acacH), methyl acetoacetate (macacH) or ethyl acetoacetate (eacacH) have been synthesized by the reaction of VOSO4⋅5H2O and the ligands given above in aqueous-ethanol medium. The resulting complexes have been characterized on the basis of elemental analyses, vanadium determination, molar conductance and magnetic measurements, mass spectrometry, thermogravimetric analysis, infrared and electron spin resonance spectral studies. The thermal decomposition processes of two representative complexes are discussed and the order of reaction (n) and the activation energy (Ea) for the particular decomposition steps have been calculated from thermogravimetric (TG) curve. Geometry optimizations were performed with the Gaussian 09 software package by using density functional theory (DFT) methods with Becke-3–Lee–Yang–Parr (B3LYP) hybrid exchange–correlation functional and the standard LANL2MB basis set for dhaH and its complex [VO(dha)(acac)(H2O)]. Molecular surface electrostatic potentials (MSEP), vibrational frequency calculations, bond lengths, bond angles, dihedral angles, natural population analysis and calculations of molecular energies, HOMO and LUMO were made. No imaginary frequency was found in the optimized model compounds and hence ensures that the molecule is in the lowest point of the potential energy surface, that is, a energy minimum. Finally calculated results were applied to simulated Infrared spectra of the title compound which show good agreement with observed spectra. Based on experimental and theoretical data, suitable trans-octahedral structures have been proposed for these complexes.

Influence of the exchange and correlation functional on the structure of amorphous Ge2Sb2Te5

Models of the amorphous phase of GeSbTe have been generated by density functional molecular dynamics simulations with the Becke–Lee–Yang–Parr (BLYP) exchange–correlation functional. Four independent 459-atom models have been used to improve the statistical analysis of the structural properties with respect to previous work by Kim et al. [J. Appl. Phys. 113, 134302 (2013)]. Structural, electronic, and vibrational properties of the BLYP models turn out to be very similar to those generated previously with the Perdew–Burke–Ernzerhof (PBE) functional mostly used in the simulations of phase change compounds. Only a very marginal increase in the fraction of tetrahedra is observed in the BLYP models.