Valence Double Zeta Research Articles

On symmetry breaking of CH5+ ions and deuterated variants (CHxD (5-x) +): real or artefactual rotational motions?

Protonated methane, CH5 + , has unusual vibrational and rotational behavior because its three nonequivalent equilibrium structures have nearly identical energies and its five protons scramble freely. Although a few theoretical papers have been published on the quantum mechanics of these systems, a better understanding requires spectral and conformational analysis. Post hartree-fock, Moller-Plesset and DFT calculations with the correlation consistent polarized valence double and triple zeta basis sets have been accomplished for estimating the thermodynamic data and zero-point energies of CH x D (5-x) + .The present results indicates the normal modes agree with qualitative of CH x D (5-x) + which modes 10 indicates CH 5 + is highly fluxional and has a complex spectrum while the C-H bonds which are broken and reformed all the time. The spectrum of mode 12 is highly complex with red-and some blue shifts. In particular, modes 8 and 10 be attributed to the rapid coupling of the CH-stretching normal mode to motions more closely related to isomerization, i.e., bending or rocking. There has thus been a long debate whether CH5+ has a structure at all or not and is it real rotational motions or artefactual.

Crystal structure, vibrational spectra, optical and DFT studies of poly[bis(L-methionine)-κS:O cadmium (II) di-μ-thiocyanato- κ2N:S; κ2S:N

Crystal structure, FT-Raman, IR and UV–vis spectroscopy have been applied to investigate the potential nonlinear optical (NLO) material of [Cd(SCN)2(C5H11NO2S)2]n. Crystal structure of [Cd(SCN)2(C5H11NO2S)2]n shows that the one-dimensional chain is propagated through doubly bridging thiocyanate and l-methionine (C5H11NO2S) acts as terminal ligand. These chains are linked together by mean of NH⋯N and NH⋯O hydrogen bonds. Optimized molecular geometry, atomic Mulliken charges, harmonic vibrational frequencies, energies of frontier molecular orbitals (EHOMO and ELUMO), energy band gap (EHOMO–ELUMO), chemical potential (μ), chemical hardness (η), global electrophilicity index(ω) dipole moment, linear polarizability, and first order hyperpolarizability were calculated by Density functional theory (DFT) using B3LYP method with double-zeta valence (LANL2DZ). The calculated structural parameters (bond lengths and angles) are in good agreement with the experimental XRD data. DFT is also applied to explore the nonlinear optical properties of this material. This compound exhibits non-zero static first hyperpolarizabilities values so it might have microscopic NLO behavior. A detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Good consistency is found between the calculated results and experimental data for the IR and Raman spectra.

Ultra-small Ag clusters in zeolite A4: Antibacterial and thermochromic applications

The physical and chemical properties of metal clusters depend on their atomic structure, therefore, it is important to determine the lowest-energy structures of the clusters in order to understand and utilize their properties. In this work, we use the Density Functional Theory (DFT) at the generalized gradient approximation level Becke's three-parameter and the gradient corrected functional of Lee, Yang and Puar (B3LYP) in combination with the basis set LANL2DZ (the effective core potentials and associated double-zeta valence) to determine some of the structural, electronic and vibrational properties of the planar silver clusters (Agn clusters n = 2–24). Additionally, the study reports the experimental synthesis of small silver clusters in synthetic zeolite A4. The synthesis was possible using the ion exchange method with some precursors like silver nitrate (AgNO3) and synthetic zeolite A4. The silver clusters in zeolite powder underwent thermal treatment at 450 °C to release the remaining water or humidity on it. The morphology of the particles was determined by Transmission Electron microscopy. The nanomaterials obtained show thermochromic properties. The structural parameters were correlated theoretically and experimentally.

Effective charges of ionic liquid determined self-consistently through combination of molecular dynamics simulation and density-functional theory.

A self-consistent scheme combining the molecular dynamics (MD) simulation and density functional theory (DFT) was recently proposed to incorporate the effects of the charge transfer and polarization of ions into non-poralizable force fields of ionic liquids for improved description of energetics and dynamics. The purpose of the present work is to analyze the detailed setups of the MD/DFT scheme by focusing on how the basis set, exchange-correlation (XC) functional, charge-fitting method or force field for the intramolecular and Lennard-Jones interactions affects the MD/DFT results of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide ( [C1mim][NTf2]) and 1-ethyl-3-methylimidazolium glycinate ( [C2mim][Gly]). It was found that the double-zeta valence polarized or larger size of basis set is required for the convergence of the effective charge of the ion. The choice of the XC functional was further not influential as far as the generalized gradient approximation is used. The charge-fitting method and force field govern the accuracy of the MD/DFT scheme, on the other hand. We examined the charge-fitting methods of Blöchl, the iterative Hirshfeld (Hirshfeld-I), and REPEAT in combination with Lopes et al.'s force field and general AMBER force field. There is no single combination of charge fitting and force field that provides good agreements with the experiments, while the MD/DFT scheme reduces the effective charges of the ions and leads to better description of energetics and dynamics compared to the original force field with unit charges. © 2017 Wiley Periodicals, Inc.

Segmented all-electron Gaussian basis sets of double and triple zeta qualities for Fr, Ra, and Ac

Segmented all-electron basis sets of valence double and triple zeta qualities plus polarization functions for the elements Fr, Ra, and Ac are generated using non-relativistic and Douglas-Kroll-Hess (DKH) Hamiltonians. The sets are augmented with diffuse functions with the purpose to describe appropriately the electrons far from the nuclei. At the DKH-B3LYP level, first atomic ionization energies and bond lengths, dissociation energies, and polarizabilities of a sample of diatomics are calculated. Comparison with theoretical and experimental data available in the literature is carried out. It is verified that despite the small sizes of the basis sets, they are yet reliable.

All-electron Gaussian basis sets of double zeta quality for the actinides.

For the actinides, two segmented all-electron basis sets of valence double zeta quality plus polarization functions (DZP) are developed. One of them must be used along with the non-relativistic Hamiltonian, whereas the other with the Douglas-Kroll-Hess (DKH) one. Adding diffuse functions of s, p, d, f, and g symmetries to the non-relativistic and relativistic sets, augmented basis sets are developed. These functions are essential to describe correctly electrons far away from the nuclei. For some compounds, geometric parameters, atomic charges and valence orbital populations of the actinides, and bond dissociation energies are calculated using the Becke 3-parameter (exchange) and the Lee, Yang, and Parr (correlation) functional in conjunction with the DZP-DKH basis set. For Am and No, the static electric mean dipole polarizabilities are also reported. Comparison with benchmark theoretical and experimental values found in the literature is carried out. It is verified that the performances of the relativistic compact size basis sets generated in this work are regular, efficient, and reliable. They will be extremely helpful in molecular property calculations that need explicitly to consider the core electrons.

Is the bonding cumulenic or polyacetylenic in nonatetraynylidene?

To answer the entitled question, the equilibrium geometry of the linear triplet ground electronic state X∼3Σg- of nonatetraynylidene (1), HC9H, has been theoretically investigated at various levels of theory. The relative energies, optimal geometry parameters, expectation values of S2, rotational constant, spin densities, and harmonic vibrational frequencies with respect to both restricted open-shell Hartree-Fock (ROHF) and unrestricted HF (UHF) at different levels are examined. The methods employed are HF Self-Consistent Field (SCF), Møller-Plesset perturbation level of theory until second-order (MP2), coupled-cluster singles and doubles (CCSD), and CCSD with perturbative triple excitations (CCSD(T)). Correlation consistent polarized valence double and triple zeta (cc-pVXZ; X=D and T) basis sets are used in all calculations and frozen-core approximation is utilized in all post-SCF calculations. Population analysis of the spin densities at CC levels suggest that several valence structures are possible for 1 implying more polyacetylenic character rather than the cumulenic biradical.

The equilibrium geometries of heptatriynylidene, cyclohepta-1,2,3,4-tetraen-6-yne, and heptahexaenylidene

The equilibrium geometries of heptatriynylidene (1), cyclohepta-1,2,3,4-tetraen-6-yne (2), and heptahexaenylidene (3) have been theoretically investigated at various level of theories. The methods employed are Møller–Plesset perturbation level of theory until second-order, coupled-cluster singles and doubles (CCSD), and CCSD with perturbative triple excitations [CCSD(T)]. Correlation consistent polarized valence double and triple zeta (cc-pVXZ; X=D and T) basis sets are used in all calculations, which are compatible with the frozen-core approximation entreated in this study. The relative energies of the ground triplet electronic state (X∼3Σg-) of 1 – the most stable isomer of C7H2 – to the ground singlet electronic states of 2 (X∼1A1) and 3 (X∼1A1) have also been estimated at different levels. With zero-point vibrational energy corrections, 2 and 3 are found to lie ∼12.27 and ∼20.62kcalmol−1, respectively, above 1 at the highest level of theory (CCSD(T)/cc-pVTZ). While 1 and 3 are observed in the laboratory, 2 is a hypothetical molecule hitherto. Since the optimal geometry of 2 suggests the presence of biradical character, the singlet–triplet (X∼1A1–3B1) energy gap for isomer 2 was also calculated at various levels. The ab initio data presented here may be useful for the laboratory detection of 2 and astronomical detection of2and3.

All-electron double zeta basis sets for the lanthanides: Application in atomic and molecular property calculations

Segmented all-electron basis sets of valence double zeta quality plus polarization functions (DZP) for the elements from Ce to Lu are generated to be used with the non-relativistic and Douglas–Kroll–Hess (DKH) Hamiltonians. At the B3LYP level, the DZP-DKH atomic ionization energies and equilibrium bond lengths and atomization energies of the lanthanide trifluorides are evaluated and compared with benchmark theoretical and experimental data reported in the literature. In general, this compact size set shows to have a regular, efficient, and reliable performance. It can be particularly useful in molecular property calculations that require explicit treatment of the core electrons.

Breathing Raman modes in Ag2S nanoparticles obtained from F9 zeolite matrix

Ag2S nanoparticles were synthesized with a combination of synthetic F9, silver nitrate (AgNO3) and monohydrated sodium sulfide (Na2S9H2O). An ionic exchange was achieved via hydrothermal reaction. Nanoparticles with a predominant size ranging from 2 to 3nm were obtained through Transmission Electron Microscopy (TEM). The nanoparticles feature a phase P21/n (14) monoclinic structure. A Raman band can be observed at around 250cm−1 in the nanoparticles. Furthermore, the vibrational properties and stability parameters of the clusters (AgS)n, (with n=2–9) were studied by the Density Functional Theory (DFT). The approximation levels used with DFT were: Local Spin Density Approximation (LSDA) and Becke’s three-parameter and the gradient corrected functional of Lee, Yang and Puar (B3LYP) in combination with the basis set LANL2DZ (the effective core potentials and associated double-zeta valence). The Radial Breathing Mode (RBM) for B3LYP was found between 227 and 295cm−1 as well as in longer wavelengths for LSDA.

Estimating the Impact of an All-Electron Basis Set and Scalar Relativistic Effects on the Structure, Stability, and Reactivity of Small Copper Clusters

Basis sets of valence double and quadruple zeta qualities and the Douglas-Kroll-Hess (DKH) approximation are used to estimate the impact of an all-electron basis set and scalar relativistic effects on the structure, stability, and electronic properties of small neutral copper clusters (Cun, n ≤ 8). At the Becke three-parameter for exchange and Perdew-Wang 91 for correlation (B3PW91) non-relativistic and relativistic levels of theory, the bond length, binding energy, ionization potential, electron affinity, chemical potential, chemical hardness, and electrophilicity index are calculated. The results show that the agreement with experiment improves significantly when the DKH Hamiltonian combined with an all-electron relativistic basis set is used. Polarizabilities and hyperpolarizability are also reported. At the B3PW91 level, all-electron basis sets are shown to be more reliable than effective core potential valence basis sets in the determination of the second hyperpolarizability of copper clusters.

Quantum chemical studies on structural, vibrational, NBO and hyperpolarizability of N-(1,1-Dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid

The FTIR and FT-Raman spectra of N-(1,1-Dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid were recorded in the regions 4000–400cm−1 and 4000–50cm−1 respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using Hartee–Fock and density functional method (B3LYP) with the correlation consistent-polarized valence double zeta (cc-pVDZ) basis set. The most stable conformer was optimized and the structural and vibrational parameters were determined based on this. With the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. Thermodynamic properties and Mulliken charges were calculated using both Hartee–Fock and density functional method using the cc-pVDZ basis set and compared. The calculated HOMO–LUMO energy gap revealed that charge transfer occurs within the molecule. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge Including Atomic Orbital (GIAO) method and were compared with experimental results. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using Natural Bond Orbital (NBO) analysis. The first order hyperpolarizability (β) and Molecular Electrostatic Potential (MEP) of the molecule was computed using DFT calculations. The electron density based local reactivity descriptor such as Fukui functions were calculated to explain the chemical reactivity site in the molecule.

DFT analysis on the molecular structure, vibrational and electronic spectra of 2-(cyclohexylamino)ethanesulfonic acid

The FTIR and FT-Raman spectra of 2-(cyclohexylamino)ethanesulfonic acid were recorded in the regions 4000–400cm−1 and 4000–50cm−1 respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using Hartee–Fock and Density functional method (B3LYP) with the correlation consistent-polarized valence double zeta (cc-pVDZ) basis set and 6-311++G(d,p) basis set. The most stable conformer was optimized and the structural and vibrational parameters were determined based on this. The complete assignments were performed based on the Potential Energy Distribution (PED) of the vibrational modes, calculated using Vibrational Energy Distribution Analysis (VEDA) 4 program. With the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. Thermodynamic properties and Atomic charges were calculated using both Hartee–Fock and density functional method using the cc-pVDZ basis set and compared. The calculated HOMO–LUMO energy gap revealed that charge transfer occurs within the molecule. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge Including Atomic Orbital (GIAO) method and were compared with experimental results. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using Natural Bond Orbital (NBO) analysis. The first order hyperpolarizability (β) and Molecular Electrostatic Potential (MEP) of the molecule was computed using DFT calculations. The electron density based local reactivity descriptor such as Fukui functions were calculated to explain the chemical reactivity site in the molecule.

DFT simulations and vibrational spectra of 2-amino-2-methyl-1,3-propanediol

The FTIR and FT-Raman spectra of 2-amino-2-methyl-1,3-propanediol were recorded in the regions 4000–400cm−1 and 4000–50cm−1 respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using Hartee-Fock and density functional method (B3LYP) with the augmented-correlation consistent-polarized valence double zeta (aug-cc-pVDZ) basis set. The most stable conformer was optimized and the structural and vibrational parameters were determined based on this. The complete assignments were performed on the basis of the Potential Energy Distribution (PED) of the vibrational modes, calculated using Vibrational Energy Distribution Analysis (VEDA) 4 program. With the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. Thermodynamic properties and Mulliken charges were calculated using both Hartee-Fock and density functional method using the aug-cc-pVDZ basis set and compared. The calculated HOMO-LUMO energy gap revealed that charge transfer occurs within the molecule. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge-Independent Atomic Orbital (GIAO) method and were compared with experimental results.

All-electron double zeta basis sets for the most fifth-row atoms: Application in DFT spectroscopic constant calculations

Segmented all-electron contracted double zeta valence plus polarization function (DZP) basis sets for the elements Cs, Ba, La, from Hf to Ir, and from Au to Rn are constructed for using in conjunction with the non-relativistic and Douglas–Kroll–Hess (DKH) Hamiltonians. Using the B3LYP hybrid functional, the performance of the DZP–DKH basis set is assessed for predicting atomic ionization energy as well as spectroscopy constants of some compounds. Despite its compact size, this set demonstrates consistent, efficient, and reliable performance and will be especially useful in calculations of molecular properties that require explicit treatment of the core electrons.

Basis Set Convergence on Static Electric Dipole Polarizability Calculations of Alkali-Metal Clusters

A hierarchical sequence of all-electron segmented contracted basis sets of double, triple and quadruple zeta valence qualities plus polarization functions augmented with diffuse functions for the atoms from H to Ar was constructed. A systematic study of basis sets required to obtain reliable and accurate values of static dipole polarizabilities of lithium and sodium clusters (n = 2, 4, 6 and 8) at their optimized equilibrium geometries is reported. Three methods are examined: Hartree-Fock (HF), second-order Mfller-Plesset perturbation theory (MP2), and density functional theory (DFT). By direct calculations or by fitting the directly calculated values through one extrapolation scheme, estimates of the HF, MP2 and DFT complete basis set limits were obtained. Comparison with experimental and theoretical data reported previously in the literature is done.

Ab initio non-adiabatic molecular dynamics

Adiabatic nuclear potential energy surfaces (PESs) defined via the Born-Oppenheimer (BO) approximation are a fundamental concept underlying chemical reactivity theory. For a wide range of excited-state phenomena such as radiationless decay, energy and charge transfer, and photochemical reactions, the BO approximation breaks down due to strong couplings between two or more BO PESs. Non-adiabatic molecular dynamics (NAMD) is the method of choice to model these processes. We review new developments in quantum-classical dynamics, analytical derivative methods, and time-dependent density functional theory (TDDFT) which have lead to a dramatic expansion of the scope of ab initio NAMD simulations for molecular systems in recent years. We focus on atom-centered Gaussian basis sets allowing highly efficient simulations for molecules and clusters, especially in conjunction with hybrid density functionals. Using analytical derivative techniques, forces and derivative couplings can be obtained with machine precision in a given basis set, which is crucial for accurate and stable dynamics. We illustrate the performance of surface-hopping TDDFT for photochemical reactions of the lowest singlet excited states of cyclohexadiene, several vitamin D derivatives, and a bicyclic cyclobutene. With few exceptions, the calculated quantum yields and excited state lifetimes agree qualitatively with experiment. For systems with ∼50 atoms, the present Turbomole implementation allows NAMD simulations with 0.2-0.4 ns total simulation time using hybrid density functionals and polarized double zeta valence basis sets on medium-size compute clusters. We close by discussing open problems and future directions.

A simple DFT-based diagnostic for nondynamical correlation

We propose a simple DFT-based diagnostic for nondynamical correlation effects, namely Aλ = (1 - TAE[XλC]/TAE[XC])/λ where TAE stands for the molecular total atomization energy, XC is a pure-DFT exchange-correlation functional, and XλC represents the corresponding hybrid with 100λ % Hartree–Fock-type exchange. The diagnostic is a good predictor for sensitivity of energetics to the level of theory, unlike most wavefunction- based diagnostics. For GGA functionals, Aλ values approaching unity indicate severe nondynamical correlation, while values between 0 and about 0.1 indicate systems where correlation is predominantly dynamical in character (or entirely absent). The diagnostic is only weakly sensitive to the basis set (beyond polarized valence double zeta) and can easily be applied to problems beyond the practical reach of wavefunction ab initio methods required for other diagnostics. We also propose a simple measure for the importance of dynamic correlation..

Synthesis, Spectroscopy, Theoretical, and Electrochemical Studies of Zn(II), Cd(II), and Hg(II) Azide and Thiocyanate Complexes of a New Symmetric Schiff-Base Ligand

Synthesis of zinc(II)/cadmium(II)/mercury(II) thiocyanate and azide complexes of a new bidentate Schiff-base ligand (L) with general formula of MLX2(M = Zn(II), Cd(II), and Hg(II)) in ethanol solution at room temperature is reported. The ligand and metal complexes were characterized by using ultraviolet-visible (UV-visible), Fourier transform infrared (FT-IR),1H- and13C-NMR spectroscopy and physical characterization, CHN analysis, and molar conductivity.1H- and13C-NMR spectra have been studied in DMSO-d6. The reasonable shifts of FT-IR and NMR spectral signals of the complexes with respect to the free ligand confirm well coordination of Schiff-base ligand and anions in an inner sphere coordination space. The conductivity measurements as well as spectral data indicated that the complexes are nonelectrolyte. Theoretical optimization on the structure of ligand and its complexes was performed at the Becke’s three-parameter hybrid functional (B3) with the nonlocal correlation of Lee-Yang-Parr (LYP) level of theory with double-zeta valence (LANL2DZ) basis set using GAUSSIAN 03 suite of program, and then some theoretical structural parameters such as bond lengths, bond angles, and torsion angles were obtained. Finally, electrochemical behavior of ligand and its complexes was investigated. Cyclic voltammograms of metal complexes showed considerable changes with respect to free ligand.

Self-assembly and photophysical properties of a minuscule tailed perylene bisimide

N,N′- Di(octyl)perylene-3,4,9,10-tetracarboxylic diimide was synthesized and its self-assembly and photophysical behavior were evaluated. Thermal stability and electrochemical behavior of the compound were analyzed using thermogravimetric analysis, differential scanning calorimetry and cyclic voltammetric (CV) techniques. The structure was optimized at the double zeta valence level of the density functional theory and the frontier orbital levels were computed and equated with experimental CV values. Natural bond orbital analysis was used to correlate electron population in the lowest unoccupied molecular orbital with stacking. The morphology of the formed molecular self-assembly was investigated by scanning electron microscopy. The results indicated the linear alkyl chains hydrophobic interaction cooperative with π–π stacking between the aromatic skeleton induced in the self-assembly. The CV and computational studies supported the materials semiconductive nature.