DMC and VMC Calculations of the Electric Dipole Moment and the Ground-State Total Energy of Hydrazine Molecule Using CASINO-Code (original) (raw)
Related papers
2015
A quantum Monte Carlo (QMC) study of the electric dipole moment of hydrazine molecule using CASINO-code is presented. The variational quantum Monte Carlo (VQMC) technique used in this work employed the restricted Hartree-Fock (RHF) scheme. The components dependence of the electric dipole moment from the QMC technique is studied with a single determinant Slater-Jastrow trial wave-function obtained from the Hartree-Fock orbitals. The simulation requires that the configurations must evolve on the time scale of the electronic motion, and after equilibration, the estimated effective timestep be obtained. From our result, though the VQMC method showed much fluctuation, the technique calculated the electric dipole moment of hydrazine molecule as 2.0 D, which is in closer agreement with 1.85 D experimental value than others in literature. Thus, the result from this study is found to be precisely approaching the required order of chemical accuracy. Keywords : CASINO code, Electric dipole mom...
Journal of Molecular Liquids, 2014
The ground state (μ g ) and excited state (μ e ) dipole moments of the studied α-hydroxy phenylhydrazones are determined by using solvatochromism theory which is based on the variation of Stokes shift with solvent's relative permittivity and refractive index. Excited state dipole moments are found as larger than the ground state dipole moment due to substantial redistribution of the π-electron density in more polar excited state. External electric field (EF) effect on HOMO-LUMO gap (HLG) and dipole moment is studied by GGA level of theory. Density of states (DOS) and HOMO, LUMO plots are also investigated by GGA method. Solvent accessible surface (SAS) and molecular electrostatic potential (MEP) are visualized as a result of DFT calculations.
Molecular Electrical Properties from Quantum Monte Carlo Calculations: Application to Ethyne
Journal of Chemical Theory and Computation, 2012
We used Quantum Monte Carlo (QMC) methods to study the polarizability and the quadrupole moment of the ethyne molecule using the Jastrow-Antisymmetrised Geminal Power (JAGP) wave function, a compact and strongly correlated variational ansatz. The compactness of the functional form and the full optimization of all its variational parameters, including linear and exponential coefficients in atomic orbitals, allow us to observe a fast convergence of the electrical properties with the size of the atomic and Jastrow basis sets. Both variational results on isotropic polarizability and quadrupole moment based on Gaussian type and Slater type basis sets are very close to the Lattice Regularized Diffusion Monte Carlo values and in very good agreement with experimental data and with other quantum chemistry calculations. We also study the electronic density along the CC and C−H bonds by introducing a generalization for molecular systems of the small-variance improved estimator of the electronic density proposed by Scemama, A. Phys. Rev. E, 2007, 75, 035701).
Combined experimental and theoretical studies were conducted on the molecular structure and vibrational spectra of 4-AminoPhthalhydrazide (APH). The FT-IR and FT-Raman spectra of APH were recorded in the solid phase. The molecular geometry and vibrational frequencies of APH in the ground state have been calculated by using the ab initio HF (Hartree–Fock) and density functional methods (B3LYP) invoking 6-311+G(d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF and B3LYP method show best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of APH with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled Hartree–Fock approach for molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamentals is very small. A detailed interpretation of the NMR spectra of APH was also reported. The theoretical spectrograms for infrared and Raman spectra of the title molecule have been constructed. UV–vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time dependent density functional theory (TD-DFT) approach. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. And the temperature dependence of the thermodynamic properties of constant pressure (Cp), entropy (S) and enthalpy change (DH0?T) for APH were also determined.
Asian Journal of Chemistry, 2019
The quantum chemical calculations of organic compounds viz. (E)-1-(2,6-bis(4-chlorophenyl)-3-ethylpiperidine-4-ylidene)-2-phenyl-hydrazine (3ECl), (E)-1-(2,6-bis(4-chlorophenyl)-3-methylpiperidine-4-ylidene)-2-phenylhydrazine (3MCl) and (E)-1-(2,6-bis(4-chloro-phenyl)-3,5-dimethylpiperidine-4-ylidene)-2-phenylhydrazine (3,5-DMCl) have been performed by density functional theory (DFT) using B3LYP method with 6-311G (d,p) basis set. The electronic properties such as Frontier orbital and band gap energies have been calculated using DFT. Global reactivity descriptor has been computed to predict chemical stability and reactivity of the molecule. The chemical reactivity sites of compounds were predicted by mapping molecular electrostatic potential (MEP) surface over optimized geometries and comparing these with MEP map generated over crystal structures. The charge distribution of molecules predict by using Mulliken atomic charges. The non-linear optical property was predicted and interpre...
The Journal of Physical Chemistry a, 2003
Formic hydrazide (formylhydrazine) has been investigated by microwave spectroscopy in the 8-62 GHz spectral range, as well as by quantum chemical ab initio and density functional theory calculations made at several levels of theory. Both the ab initio and the density functional theory calculations predict that two stable forms exist for this compound, a more stable conformer having a syn-periplanar arrangement for the heavy atoms, and a less stable form where these atoms are anti-periplanar. The latter rotamer is calculated to be 10-14 kJ/mol less stable than the former, depending on the theoretical approach. The barrier height separating the two forms is calculated to be 92.2 kJ/mol at the B3LYP/cc-pVTZ level. The microwave spectra of the ground and four vibrationally excited states of the lowest torsional mode of the syn-periplanar conformer were assigned. The lowest torsional frequency was determined to be 77(15) cm -1 by relative intensity measurements. The variation of the rotational constants upon excitation of this mode and the lowest torsional frequency were fitted to a potential function of the form V(z) ) 15.6(〈z 4 〉 + 4.9〈z 2 〉) cm -1 , indicating that the heavy atoms are effectively planar at the equilibrium conformation. The dipole moment was determined to be µ a ) 1.54(2), µ b ) 1.85 , µ c ) 0 (assumed), and µ tot ) 2.41(3) D [8.04(8) × 10 -30 C m] by Stark effect measurements.
An ab initio study of the equilibrium geometry and vibrational frequencies of hydrazine
Chemical Physics Letters, 2002
Accurate optimized equilibrium geometries, harmonic frequencies and rotational constants of the gauche conform (C 2 symmetry) of hydrazine ðN 2 H 4 Þ have been calculated employing a large series of basis sets and several ab initio methods. Our best estimate computed equilibrium geometries are r NN ¼ 1:434 A A, r NH i ¼ 1:013 A A, r NHo ¼ 1:010 A A, h NNH i ¼ 111:3°, h NNHo ¼ 106:8°and h H i NNHo ¼ 89:7°. These predictions were used as reference in the analysis of the experimental and theoretical data, and we expected that the present results could guide future investigations in this direction.
The present work investigates structural and spectroscopic characteristics of (4,6-dimethyl-benzofuran-3-yl)-acetic acid hydrazide (4DBAH) through different spectroscopic methods (Infrared, Raman, and NMR) and quantum chemical computations. The quantum chemical computations are done with adequate level of theory using B3LYP from density functional with 6e311þþG(d,p) basis set. Confor-mational analysis is performed to identify the structure corresponding to local minima and local maxima from the potential energy surface (PES).The theoretically simulated and Raman wavenumbers are compared with experimental data. The complete wavenumber assignments are accomplished by the potential energy distribution (PED) of individual vibrational modes. The experimental 1 H and 13 C NMR chemical shifts are investigated and then compared with computed NMR data. The AIM and NCI analysis gives more insights into the nature of different types of interactions, both attractive and repulsive nature present in the molecule. In addition, several analyses such as NBO, NLO, FMO, MEP and thermodynamic properties have also been conducted to determine the nature of the 4DBAH.
Journal of Molecular Structure: THEOCHEM, 1988
level were performed on hydrazinecarboxamide and hydraxinecarbothioamide and on their protonated forms (at the hydrazinic amino group). The two molecules show very close structural characteristics and similar bebaviour for the process of internal rotation around the different bonds. For the groundstates of the free-bases the E-form turns out to be the more stable one, while the Z-form is more stable in the case of the cations. The energy difference between conformers indicates that, in physical conditions where an equilibrium is possible, the amount of one form should predominate. These trends are in agreement with a number of experimental results, especially those relative to hydrazinecarbothioamide, which is accurately known. In the bases the barriers for internal rotation around the C-N bonds are higher for the amino than for the hydrazino group and in the sulphur higher than in the oxygen compound, yet the transition states occur for almost perpendicular conformations. For the cations two transition states are found, one in the proximity of the perpendicular conformation and the other at the planar E-conformation, separated by a flat minimum. The energy barriers in the cations are lower than in the corresponding bases. The calculated properties enable a homogeneous picture of the chemical behaviour of these molecules to be drawn, even in the absence of exhaustive experimental studies.
Threshold-Photoelectron Spectroscopic Study of Methyl-Substituted Hydrazine Compounds
The Journal of Physical Chemistry A, 2007
The valence shell electronic structures of methylhydrazine (CH 3 NHNH 2 ), 1,1-dimethylhydrazine ((CH 3 ) 2 -NNH 2 ) and tetramethylhydrazine ((CH 3 ) 4 N 2 ) have been studied by recording threshold and conventional (kinetic energy resolved) photoelectron spectra. Ab initio calculations have been performed on ammonia and the three methyl substituted hydrazines, with the structures being optimized at the B3-LYP/6-31+G(d) level of theory. The ionization energies of the valence molecular orbitals were calculated using the Green's function method, allowing the photoelectron bands to be assigned to specific molecular orbitals. The ground-state adiabatic and vertical ionization energies, as determined from the threshold photoelectron spectra, were IE a ) 8.02 ( 0.16 eV and IE v ) 9.36 ( 0.02 eV for methylhydrazine, IE a ) 7.78 ( 0.16 eV and IE v ) 8.86 ( 0.01 eV for 1,1-dimethylhydrazine and IE a ) 7.26 ( 0.16 eV and IE v ) 8.38 ( 0.01 eV for tetramethylhydrazine. Due to the large geometry change that occurs upon ionization, these IE a values are all higher than the true thresholds. New features have been observed in the inner valence region and these have been compared with similar structure in the spectrum of hydrazine. The effect of resonant autoionization on the threshold photoelectron yield is discussed. New heats of formation (∆ f H) are proposed for the three hydrazines on the basis of G3 calculations: 107, 94, and 95 kJ/mol for methylhydrazine, 1,1-dimethyhydrazine and tetramethylhydrazine, respectively. The previously reported ∆ f H for tetramethylhydrazine is shown to be