Finite Field Approach Research Articles

Theoretical study of nonlinear optical properties of some azoic dyes

In this paper we presented semi-empirical PM3, ab-initio (HF, MP2) and DFT (B3LYP, B3PW91) calculation of the dipole moment, polarizability, and first hyperpolarizability of some azoics dyes derivatives which have electron donor and electron acceptor groups on either sides. The first hyperpolarizability of these molecules was calculated with PM3 method, HF/6-31G**, HF/6-31+G**, HF/6-31++G**, DFT with B3LYP and B3PW91 functional, and MP2/6-31++G** based on finite field approach using GAUSSIAN03 program. The effects of the intramolecular charge transfer (ICT) from the donor to the acceptor groups on the molecular geometry and atomic charge distribution of these NLO chromophores are derived from its HF, MP2 and DFT calculations. The variation of this property has also been correlated to E (HOMO-LUMO) gap and to the nature of the highest occupied molecular orbital HOMO and the lowest unoccupied molecular orbital HOMO. The study reveals that the azoics dyes derivatives have large hyperpolarizability values; hence they may be used in the development of nonlinear optical materials.

Small and efficient basis sets for the evaluation of accurate interaction-induced linear and non-linear electric properties in model hydrogen-bonded complexes

Interaction-induced electric dipole moment, polarisability and first hyperpolarisability are investigated in model hydrogen-bonded clusters built of hydrogen fluoride molecules organised in three linear chains parallel to each other. The properties are evaluated within the finite field approach, using the second order Møller–Plesset method, and the LPol-m (m = ds, dl) and the optical rotation prediction (ORP) basis sets. These bases and correlation method are selected after a systematic basis set and correlation method convergence study carried out on the smallest of the complexes and taking properties obtained with Dunning's bases and the coupled cluster singles and doubles (CCSD) and the CCSD including connected triple corrections (CCSD(T)) methods as reference. Results are analysed in terms of many-body and cooperative effects.

Molecular structure, First-order hyperpolarizability and HOMO-LUMO studies of L- Histidinium Dinitrate

The geometric parameters and hyperpolarizabilities of a nonlinear optical material L- Histidinium Dinitrate (LHDN) was investigated by density functional theory and presented. The compound crystallizes in the noncentro symmetric space group P212121 of orthorhombic system. The first order hyperpolarizability (β) of this molecular system is calculated using B3LYP/6-31G (d,p) method on the finite-field approach. The calculation results also show that the LHDN molecule might have microscopic nonlinear optical behavior with non zero values. The Optical absorption spectrum and second harmonic generation were investigated. The calculated HOMO and LUMO energies showed that charge transfer occurs within the molecule.

Spectroscopic [FT-IR and FT-Raman] and theoretical [UV–Visible and NMR] analysis on α-Methylstyrene by DFT calculations

In the present research work, the FT-IR, FT-Raman and 13C and 1H NMR spectra of the α-Methylstyrene were recorded. The observed fundamental frequencies in finger print as well as functional group regions were assigned according to their uniqueness region. The Gaussian computational calculations are carried out by HF and DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The impact of the presence of vinyl group in phenyl structure of the compound is investigated. The modified vibrational pattern of the molecule associated vinyl group was analyzed. Moreover, 13C NMR and 1H NMR were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP methods and the 6-311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed.

ROVIBRATIONAL LINE LISTS FOR NINE ISOTOPOLOGUES OF THE CO MOLECULE IN THE X 1 Σ + GROUND ELECTRONIC STATE

Extensive rovibrational line lists were computed for nine isotopologues of the CO molecule, namely, {sup 12}C{sup 16}O, {sup 12}C{sup 17}O, {sup 12}C{sup 18}O, {sup 13}C{sup 16}O, {sup 13}C{sup 17}O, {sup 13}C{sup 18}O, {sup 14}C{sup 16}O, {sup 14}C{sup 17}O, and {sup 14}C{sup 18}O in the ground electronic state with v ≤ 41, Δv ≤ 11, and J ≤ 150. The line intensity and position calculations were carried out using a newly determined piece-wise dipole moment function (DMF) in conjunction with the wavefunctions calculated from an experimentally determined potential energy function from Coxon and Hajigeorgiou. A direct-fit method that simultaneously fits all the reliable experimental rovibrational matrix elements has been used to construct the dipole moment function near equilibrium internuclear distance. In order to extend the amount and quality of input experimental parameters, new Cavity Ring Down Spectroscopy experiments were carried out to enable measurements of the lines in the 4-0 band with low uncertainty as well as the first measurements of lines in the 6-0 band. A new high-level ab initio DMF, derived from a finite field approach has been calculated to cover internuclear distances far from equilibrium. Accurate partition sums have been derived for temperatures up to 9000 K. In additionmore » to air- and self-induced broadening and shift parameters, those induced by CO{sub 2} and H{sub 2} are now provided for planetary applications. A complete set of broadening and shift parameters was calculated based on sophisticated extrapolation of high-quality measured data. The line lists, which follow HITRAN formalism, are provided as supplementary material.« less

Molecular vibrational investigation [FT-IR, FT-Raman, UV–Visible and NMR] on Bis(thiourea) Nickel chloride using HF and DFT calculations

In the present research work, the FT-IR, FT-Raman spectra of the Bis(thiourea) Nickel chloride (BTNC) were recorded and analyzed. The observed fundamental frequencies in finger print and functional group regions were assigned according to their uniqueness region. The computational calculations were carried out by HF and DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The present organo-metallic compound was made up of covalent and coordination covalent bonds. The modified vibrational pattern of the complex molecule associated with ligand group was analyzed. Furthermore, the 13C NMR and 1H NMR spectral data were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP/6-311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A investigation on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed.

Crystal growth and properties of NLO optical crystal – Butylated Hydroxy Toluene (BHT)

Crystallographic, experimental and theoretical density functional theory (DFT) of Butylated Hydroxy Toluene (BHT) are investigated. The grown crystals were identified by single crystal X-ray analysis. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of BHT is calculated using B3LYP/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO/NLMO analysis. The molecular electrostatic potential (MESP) mapping is very useful in the investigation of the molecular structure with its physiochemical property relationship. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charge is also calculated. Because of vibrational analysis, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV–Vis spectra and electronic absorption properties are explained and illustrated from the frontier molecular orbitals. The grown crystals were characterized by measuring their thermal properties by Differential Thermal Analysis (DTA) and Thermo Gravimetric Analysis (TGA) measurements.

Quantum chemical calculations on elucidation of molecular structure and spectroscopic insights on 2-amino-4-methoxy-6-methylpyrimidine and 2-amino-5-bromo-6-methyl-4-pyrimidinol – A comparative study

The FTIR and FT-Raman spectra of 2-amino-4-methoxy-6-methylpyrimidine (AMMP) and 2-amino-5-bromo-6-methyl-4-pyrimidinol (ABMP) have been recorded in the region 4000–450 and 4000–100cm−1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of AMMP and ABMP were obtained by the density functional theory (DFT) using 6-311++G∗∗ basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The 1H and 13C NMR spectra have been recorded. The 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method. The theoretical UV–visible spectrum of the compound using TD-DFT method and the electronic properties, such as HOMO and LUMO energies, are performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) and its related components of AMMP and ABMP are calculated using DFT/6-311++G∗∗ method on the finite-field approach. The natural atomic charges of the molecules were also discussed. The change in electron density (ED) in the σ∗ antibonding orbitals and stabilization energies E(2) have been calculated by natural bond orbital (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interactions.

Quantum chemical density functional theory studies on the molecular structure and vibrational spectra of mannitol

A collective experimental and theoretical study was conducted on the molecular structure and vibrational spectra of mannitol. The FT-IR and FT-Raman spectra of mannitol were recorded in the solid phase. The molecular geometry, vibrational frequencies, thermodynamic functions and atomic charges of mannitol in the ground state have been calculated by using the ab initio HF (Hartree–Fock) and density functional methods (B3LYP) invoking cc-pVDZ basis set. The complete vibrational assignments were performed on the basis of Total Energy Distribution (TED) of the vibrational modes. The UV absorption spectra of the title compound dissolved in water. Natural bond orbital analysis has been carried out to explain the charge transfer or delocalization of charge due to the intra-molecular interactions. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by GIAO methods. The first order hyperpolarizability (β0) of this novel molecular system and related properties (β, α0 and Δα) of mannitol are calculated using B3LYP/cc-pVDZ and HF/cc-pVDZ methods on the finite-field approach. By using TD-DFT calculation, electronic absorption spectra of the title compound have been predicted and a good agreement with experimental one is established. In addition, the molecular electrostatic potential (MEP) have been investigated using theoretical calculations, the calculated HOMO and LUMO energies shows that the charge transfer within the molecule.

Vibrational spectroscopic studies, normal co-ordinate analysis, first order hyperpolarizability, HOMO–LUMO of midodrine by using density functional methods

The FTIR (4000–400cm−1), FT-Raman (4000–100cm−1) and UV–Visible (400–200nm) spectra of midodrine were recorded in the condensed state. The complete vibrational frequencies, optimized geometry, intensity of vibrational bands and atomic charges were obtained by using Density Functional Theory (DFT) with the help of 6-311++G(d,p) basis set. The first order hyperpolarizability (β) and related properties (μ, α and Δα) of this molecular system were calculated by using DFT/6-311++G(d,p) method based on the finite-field approach. The assignments of the vibrational spectra have been carried out with the help of Normal Co-ordinate Analysis (NCA) following the scaled quantum mechanical force methodology. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using NBO analysis. From the recorded UV–Visible spectrum, the electronic properties such as excitation energies, oscillator strength and wavelength are calculated by DFT in water and gas methods using 6-311++G(d,p) basis set. The calculated HOMO and LUMO energies confirm that charge transfer occurs within the molecule. Besides MEP, NLO and thermodynamic properties were also calculated and interpreted. The electron density-based local reactivity descriptor such as Fukui functions was calculated to explain the chemical selectivity or reactivity site in midodrine.

DFT computational analysis of piracetam

Density functional theory calculation with B3LYP using 6-31G(d,p) and 6-31++G(d,p) basis set have been used to determine ground state molecular geometries. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of piracetam is calculated using B3LYP/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO/NLMO analysis. The calculation of first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. Molecular electrostatic potential (MEP) at a point in the space around a molecule gives an indication of the net electrostatic effect produced at that point by the total charge distribution of the molecule. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charge is also calculated. Because of vibrational analysis, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV–Vis spectra and electronic absorption properties are explained and illustrated from the frontier molecular orbitals.

Vibrational assignment, HOMO–LUMO and NBO analysis of (2S)-2-[(2-{[(2S)-1-hydroxybutan-2-yl]amino}ethyl)amino]butan-1-ol by density functional theory

The FTIR and FT-Raman spectra of (2S)-2-[(2-{[(2S)-1-hydroxybutan-2-yl]amino}ethyl)amino]butan-1-ol have been recorded in the region 4000–400cm−1and 4000–100cm−1 respectively. Utilizing the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental vibrational modes of the compound were carried out. The optimized molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering were calculated by HF and density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee–Yang–Parr) quantum chemical method with 6-31G(d,p), 6-31+G(d,p), 6-31++G(d,p) basis sets. The theoretical and optimized geometric parameters and vibrational frequencies have been found in good agreement with the corresponding experimental data and results in the literature. Ultraviolet–visible spectrum of the title molecule was recorded and has been calculated using TD-DFT method. The first-order hyperpolarizability (βo) and other related properties (μ, αo) of the compound are calculated using DFT method on a finite field approach. The most stable geometry of the compound under investigation has been determined from the potential energy scan. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital analysis (NBO). Besides, molecular electrostatic potential (MESP), HOMO and LUMO analysis, Mulliken population analysis and several other thermodynamic properties were performed by HF and DFT method.

Experimental and theoretical (FT-IR, FT-Raman, UV–vis, NMR) spectroscopic analysis and first order hyperpolarizability studies of non-linear optical material: (2E)-3-[4-(methylsulfanyl) phenyl]-1-(4-nitrophenyl) prop-2-en-1-one using density functional theory

A combined experimental and theoretical investigation on FT-IR, FT-Raman, NMR, UV–vis spectra of a chalcone derivative (2E)-3-[4-(methylsulfanyl) phenyl]-1-(4-nitrophenyl) prop-2-en-1-one (4N4MSP) has been reported. 4N4MSP has two planar rings connected through conjugated double bond and it provides a necessary configuration to show non-linear optical (NLO) response. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) with B3LYP functional and 6-311++G(d,p) basis set combination. The analysis of the fundamental modes was made with the help of potential energy distribution (PED). Molecular electrostatic potential (MEP) surface was plotted over the geometry primarily for predicting sites and relative reactivities towards electrophilic and nucleophilic attack. The delocalization of electron density of various constituents of the molecule has been discussed with the aid of NBO analysis. The electronic properties, such as excitation energies, oscillator strength, wavelengths, HOMO and LUMO energies, were calculated by time-dependent density functional theory (TD-DFT) and the results complement the experimental findings. The recorded and calculated 1H chemical shifts in gas phase and MeOD solution are gathered for reliable calculations of magnetic properties. Thermodynamic properties like heat capacity (C°p,m), entropy (S°m), enthalpy (H°m) have been calculated for the molecule at the different temperatures. Based on the finite-field approach, the non-linear optical (NLO) parameters such as dipole moment, mean polarizability, anisotropy of polarizability and first order hyperpolarizability of 4N4MSP molecule are calculated. The predicted first hyperpolarizability shows that the molecule has a reasonably good nonlinear optical (NLO) behavior.

Molecular structure, vibrational spectroscopic, hyperpolarizability, natural bond orbital analysis, frontier molecular orbital analysis and thermodynamic properties of 2,3,4,5,6-pentafluorophenylacetic acid

The FT-IR (4000–400cm−1) and FT-Raman spectra (3500–100cm−1) of 2,3,4,5,6-pentafluorophenylacetic acid (PAA) have been recorded. Density functional theory calculation with LSDA/6-31+G(d,p) and B3LYP/6-31+G(d,p) basis sets have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman intensities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of PAA are calculated using B3LYP/6-31+G(d,p) method on the finite-field approach. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within this molecule. Mulliken population analysis on atomic charges is also calculated. Thermodynamic properties (heat capacity, enthalpy, Gibb’s free energy and entropy) of the title compound at different temperatures were calculated.

Experimental and theoretical investigation of the molecular structure, conformational stability, hyperpolarizability, electrostatic potential, thermodynamic properties and NMR spectra of pharmaceutical important molecule: 4′-Methylpropiophenone

Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra) of 4′-methylpropiophenone (MPP). The FT-IR and FT-Raman spectra of 4′-methylpropiophenone (MPP) have been recorded in the region 4000–400cm−1 and 3500–100cm−1, respectively. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the infrared and Raman spectra of MPP are also reported based on total energy distribution (TED). The observed and the calculated frequencies are found to be in good agreement. The 1H and 13C NMR chemical shifts have been calculated by Gauge-Independent Atomic Orbital (GIAO) method with B3LYP/6-311++G(d,p). The natural bond orbital (NBO), natural hybrid orbital (NHO) analysis and electronic properties, such as HOMO and LUMO energies, were performed by DFT approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) of the novel molecular system and related properties (βtot, α0 and Δα) of MPP are calculated using DFT/6-311++G(d,p) method on the finite-field approach. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The thermodynamic functions of the title compound were also performed at the above method and basis set.

Vibrational spectra, electronic and quantum mechanical investigations on ciprofloxacin

The Fourier transform infrared and FT-Raman spectra of ciprofloxacin have been recorded in region 4,000–400 and 4,000–100 cm−1, respectively. A complete assignment and analysis of fundamental vibrational modes of the molecule have been carried out. The observed fundamental modes have been compared with harmonic vibrational frequencies computed using density functional theory calculations by employing B3LYP functional at 6-31 G (d, p) level. The most stable geometry of compound under investigation has been determined from potential energy scan. The first-order hyperpolarizability (βo) and other related properties (μ, αo) of ciprofloxacin have been calculated using this theory on a finite field approach. UV–vis spectrum of the compound has been recorded and electronic properties, such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies have been calculated with B3LYP/6-31 G (d, p) level. These calculated energies show that charge transfer occurs within molecule. The other molecular properties like molecular electrostatic potential, Mulliken population analysis and thermodynamic properties of title compound have also been calculated.

Electronic responses of long chains to electrostatic fields: Hartree-Fock vs. density-functional theory: A model study

The response to an electrostatic field is determined through simple model calculations, within both the restricted Hartree-Fock and density functional theory methods, for long, finite as well as infinite, periodic chains. The permanent dipole moment, μ0, the polarizability, α, and the hyperpolarizabilities β and γ, calculated using a finite-field approach, are extensively analyzed. Our simple model allows for treatment of large systems and for separation of the properties into atomic and unit-cell contributions. That part of the response properties attributable to the terminations of the finite system change into delocalized current contributions in the corresponding infinite periodic system. Special emphasis is placed on analyzing the reasons behind the dramatic overestimation of the response properties found with density functional theory methods presently in common use.

Density Functional Study of Nonlinear Optical Properties of Grossly Warped Nanographene C80H30

Recently, a grossly warped nanographene C80H30 has been synthesized experimentally. Its optical properties are studied and compared with bucky ball C60, C70, and a flat nanographene C78H30 in the framework of density functional theory (DFT) with the B3LYP functional. The static polarizability α, first-order hyperpolarizability β, and second-order hyperpolarizability γ are calculated using the finite field approach. The average values of ⟨α⟩ and ⟨γ⟩ for C80H30 are 151.7 Å3 and 54.5 × 10–35 esu, respectively, much higher than those of C60 and C70. Both ⟨α⟩ and ⟨γ⟩ of planar C78H30 are higher than those of C80H30, which is consistent with the fact that the energy gap of C78H30 is smaller than that of C80H30. However, the diagonal component of α along the z axis of C80H30 is 86.2 Å3, much higher than 30.7 Å3 of C78H30. Furthermore, the values of the hyperpolarizability in the z direction (γxxzz, γyyzz, and γzzzz) of C80H30 are almost 1 order of magnitude higher than those of C78H30. The relationship between optical properties and electron delocalization in molecules indicated by aromaticity is also discussed. Our results indicate that C80H30 can be used as a promising optical material.

FT-IR, FT-Raman, UV–Vis spectral and normal coordinate analysis of chlorzoxazone

The FT-IR (4000–400cm−1) and FT-Raman spectra (3500–100cm−1) of chlorzoxazone (CHLZ) have been recorded in the condensed state. Density functional theory calculation with B3LYP/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond length and bond angle), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of CHLZ is calculated using B3LYP/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charges is also calculated. Because of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV–Vis spectra and electronic absorption properties were explained and illustrated from the frontier molecular orbitals.

Theoretical study of borazine and substituted borazines using density functional theory method

Borazine and donor–acceptor substituted borazines have been studied by density functional theory method. We have used NH2 as a donor and NO2, CN, COCl and NMe2 as acceptor groups. The geometrical parameters, vibrational frequencies, NLO properties and electronic absorption spectra have been obtained at B3LYP/6-311++G** level of theory. Calculated structural parameters and vibrational frequencies for borazine at this level of theory are in excellent agreement with the available experimental determinations. The BN stretching mode is the most intense vibrational mode observed in vibrational spectra of borazine and substituted borazines. The vibrational frequency for this mode is observed in a range of 1435 to 1585cm−1. For the calculations of first (β) and second (γ) hyperpolarizabilities, the finite field approach has been used. Direction of applied field, method and basis set dependent hyperpolarizabilities are obtained. The hyperpolarizabilities are found to be enhanced upon donor and acceptor substitution in borazine. For all the substituted borazines, the β and γ values are higher than those for the unsubstituted borazine.