Solid Hydrogen Fluoride Research Articles

Multifaceted Ion Exchange Resin-Supported Hydrogen Fluoride: A Path to Flow Hydrofluorination.

A solid anhydrous hydrogen fluoride equivalent was prepared by mixing HF gas with an inexpensive anion exchange resin (A26-HF, HF content 30% wt/wt).

Unusual hydrogen bonding in L-cysteine hydrogen fluoride.

L-Cysteine hydrogen fluoride, or bis(L-cysteinium) difluoride-L-cysteine-hydrogen fluoride (1/1/1), 2C3H8NO2S(+)·2F(-)·C3H7NO2S·HF or L-Cys(+)(L-Cys···L-Cys(+))F(-)(F(-)...H-F), provides the first example of a structure with cations of the 'triglycine sulfate' type, i.e. A(+)(A···A(+)) (where A and A(+) are the zwitterionic and cationic states of an amino acid, respectively), without a doubly charged counter-ion. The salt crystallizes in the monoclinic system with the space group P2(1). The dimeric (L-Cys···L-Cys(+)) cation and the dimeric (F(-)···H-F) anion are formed via strong O-H···O or F-H···F hydrogen bonds, respectively, with very short O···O [2.4438 (19) Å] and F···F distances [2.2676 (17) Å]. The F···F distance is significantly shorter than in solid hydrogen fluoride. Additionally, there is another very short hydrogen bond, of O-H···F type, formed by a L-cysteinium cation and a fluoride ion. The corresponding O···F distance of 2.3412 (19) Å seems to be the shortest among O-H···F and F-H···O hydrogen bonds known to date. The single-crystal X-ray diffraction study was complemented by IR spectroscopy. Of special interest was the spectral region of vibrations related to the above-mentioned hydrogen bonds.

Molecular cluster perturbation theory. I. Formalism

We present second-order molecular cluster perturbation theory (MCPT(2)), a linear scaling methodology to calculate arbitrarily large systems with explicit calculation of individual wave functions in a coupled-cluster framework. This new MCPT(2) framework uses coupled-cluster perturbation theory and an expansion in terms of molecular dimer interactions to obtain molecular wave functions that are infinite order in both the electronic fluctuation operator and all possible dimer (and products of dimers) interactions. The MCPT(2) framework has been implemented in the new SIA/Aces4 parallel architecture, making use of the advanced dynamic memory control and fine-grained parallelism to perform very large explicit molecular cluster calculations. To illustrate the power of this method, we have computed energy shifts, lattice site dipole moments, and harmonic vibrational frequencies via explicit calculation of the bulk system for the polar and non-polar polymorphs of solid hydrogen fluoride. The explicit lattice size (without using any periodic boundary conditions) was expanded up to 1000 HF molecules, with 32,000 basis functions and 10,000 electrons. Our obtained HF lattice site dipole moments and harmonic vibrational frequencies agree well with the existing literature.

Second-order many-body perturbation study of solid hydrogen fluoride under pressure

A linear-scaling, embedded-fragment, second-order many-body perturbation (MP2) method with basis sets up to aug-cc-pVTZ is applied to the antiparallel structure of solid hydrogen fluoride and deuterium fluoride under 0-20 GPa of ambient pressure. The optimized structures, including the lattice parameters and molar volume, and phonon dispersion as well as phonon density of states (DOS), are determined as a function of pressure. The basis-set superposition errors are removed by the counterpoise correction. The structural parameters at 0 GPa calculated by MP2 agree accurately with the observed, making the predicted values at higher pressures a useful pilot for future experiments. The corresponding values obtained by the Hartree-Fock method have large, systematic errors. The MP2/aug-cc-pVDZ frequencies of the infrared- and Raman-active vibrations of the three-dimensional solids are in good agreement with the observed and also justify previous vibrational analyses based on one-dimensional chain models; the non-coincidence of the infrared and Raman mode pairs can be explained as factor-group (Davydov) splitting. The exceptions are one pair of modes in the librational region, for which band assignments based on a one-dimensional chain model need to be revised, as well as the five pseudo-translational modes that exist only in a three-dimensional treatment. The observed pressure dependence of Raman bands in the stretching region, which red-shift with pressure, is accounted for by theory only qualitatively, while that in the pseudo-translational region is reproduced with quantitative accuracy. The present calculation proves to be limited in explaining the complex pressure dependence of the librational modes. The hydrogen-amplitude-weighted phonon DOS at 0 GPa is much less structured than the DOS obtained from one-dimensional models and may be more realistic in view of the also broad, structureless observed inelastic neutron scattering spectra. All major observed peaks can be straightforwardly assigned to the calculated peaks in the DOS. With increasing pressure, MP2 predicts further broadening of bands and breach of the demarcation between the pseudo-translational and librational bands.

Nuclear momentum distribution in solid and liquid HF from ab initio calculation

A calculation of nuclear momentum distribution of liquid and solid hydrogen fluoride was performed. In both systems, density functional theory generalized gradient approximation functional of Perdew, Burke, and Ernzerhof was used for the calculation: for liquid hydrogen fluoride, using an atom centered basis set for an isolated molecule with optimized geometry, and for solid hydrogen fluoride using plane-wave basis sets on optimized orthorhombic crystal cell. For liquid hydrogen fluoride, a semiclassical approach was adopted with the vibrational contribution to momentum distribution obtained from the density functional theory calculation and translational and rotational contributions calculated classically. Nuclear momentum distribution in the solid hydrogen fluoride was calculated entirely quantum mechanically using phonon dispersion and vibrational density of states calculated in the framework of plane-wave density functional theory. Theoretical results were contrasted with recently obtained results of Compton (deep inelastic) neutron scattering on liquid and solid hydrogen fluoride. In case of liquid hydrogen fluoride, almost a perfect agreement between theory and experiment was achieved within the harmonic Born-Oppenheimer approximation. For the solid system under investigation, the harmonic approximation leads to small (4%) overestimation of the square root of the second moment indicating that neutron Compton scattering technique is sensitive to proton delocalization due to hydrogen bonding in solid hydrogen fluoride.

Coupled‐cluster and many‐body perturbation study of energies, structures, and phonon dispersions of solid hydrogen fluoride

AbstractA linear‐scaling electron‐correlation method based on a truncated many‐body expansion of the energies of molecular crystals has been applied to solid hydrogen fluoride. The energies, structures, harmonic, and anharmonic frequencies of the infrared‐ and/or Raman‐active vibrations, phonon dispersions, and inelastic neutron scattering (INS) of the solid have been simulated employing an infinite, periodic, one‐dimensional zigzag hydrogen‐bonded chain model. The Hartree–Fock, second‐order Møller–Plesset (MP2), coupled‐cluster singles and doubles (CCSD), and CCSD with a noniterative triples correction [CCSD(T)] methods have been combined with the aug‐cc‐pVDZ and aug‐cc‐pVTZ basis sets and, in some instances, the counterpoise corrections of the basis‐set superposition errors. The computed structural parameters agree with the observed within 0.1–0.2 Å and a few degrees, and the anharmonic frequencies obtained by vibrational MP2 allowing two‐phonon couplings reproduce the observed frequencies semiquantitatively if the potential energy surface is obtained by a correlated theory. They support the revised infrared and Raman band assignments of librational modes made by Hirata and Iwata (J Phys Chem A 1998, 102, 8426) and provide more detailed assignments of the observed INS features. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

Comparison of three quantum chemical ab initio methods for band structure calculations: the hydrogen fluoride chain

Three different many-body wave-function-based ab initio methods for the calculation of correlated (or quasi-particle) band structures of periodic systems are presented: the local Hamiltonian approach, the incremental self-energy method, and the crystal orbital variant of the algebraic diagrammatic construction. All three methods explicitly exploit the local nature of electron correlation, and by consequently switching to representations in localized Wannier orbitals O(N) scaling could be achieved in all three cases. These methods were applied to single (HF)2 zigzag chains as found in solid hydrogen fluoride using the same geometries and basis sets. Essentially identical quasi-particle band structures were obtained, corroborating the appropriateness of the different concepts pursued in each of the presented quantum chemical correlation methods for band structures of infinite systems.

Investigation of electronic interactions in solid hydrogen fluoride

Intermolecular interactions in solid hydrogen fluoride are studied by the combined quantum chemical and X- ray diffraction method. The structure of crystalline HF is modeled by (HF)n chains (n =2, 3,...,20, by an (HF)45 cluster consisting of five (HF)9 chains, and by an (HF)108 cluster consisting of twelve (HF)9 chains with nearly zero dipole moment. The quantum chemical calculations of the clusters are performed by the semiempirical AM1 method, which is most suitable for electronic structure investigations of hydrogen fluoride, as shown by comparing the X- ray experimental and theoretical spectra. The theoretical X- ray spectra are also compared with the experimental FKα spectra of gaseous and solid hydrogen fluoride. For more detailed studies of electronic interactions in crystalline HF, fragrnent analysis of MOs of the clusters with respect to the MOs of the central molecule is carried out.

Theory of Nuclear Quadrupole Interactions in Solid Fluoromethanes with Implanted 19F* Nuclei. Coupling of HF* and Host Molecule

Abstract The Quadrupole Coupling Constant e2qQ and Asymmetry Parameter η of fluorine for fluorine-substitute methane compounds are calculated using the Hartree-Fock Roothaan procedure. Our results are compared with experimental data from measurements by the Time Differential Perturbed Angular Distribution (TDPAD) technique using excited 19F* (spin 5/2) nuclei. The theoretical e2qQ’s for the 19F* nuclei in the fluoromethanes are in good agreement with experimental results. For CH2F2 and CHClF2 molecules, where finite η are expected from symmetry considerations, our results for η are small, 0.12 and 0.05 respectively, in agreement with experimental observation. Besides the 19F* coupling constants associated with the C-F bonds in fluoromethanes, additional interesting NQI parameters, close to those in solid hydrogen fluoride, are observed in the TDPAD measurements. It is demonstrated through investigations of the total energies and electric field gradients that these additional NQI parameters for the fluoromethanes can be explained by a HF* molecule hydrogen-bonded through the hydrogen to a fluorine atom in the host molecular systems. This complexing of an ionic molecule to the host molecules in organic solids containing strongly electronegative atoms is expected to be a general feature in both implantation and conventional techniques.

ChemInform Abstract: Hydrofluorination of Unsaturated Compounds with Solid Potassium Hydrogen Fluoride in the Presence of Silicon Tetrafluoride at Room Temperature.

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Hydrofluorination of unsaturated compounds with solid potassium hydrogen fluoride in the presence of silicon tetrafluoride at room temperature

Hydrofluorination of unsaturated compounds proceeds by reaction with solid potassium hydrogen fluoride and silicon tetrafluoride to afford the corresponding fluorides in high yields.

Poly-4-vinylpyridinium Poly(Hydrogen Fluoride): A Solid Hydrogen Fluoride Equivalent Reagent

Poly-4-vinylpyridinium poly(hydrogen fluoride) (PVPHF), containing 35-60% hydrogen fluoride by weight, was prepared as a solid hydrogen fluoride equivalent reagent. PVPHF with 60% hydrogen fluoride by weight was found to be a versatile fluorinating agent for the hydrofluorination and bromofluorination of alkenes and alkynes, fluorination of alcohols as well as other fluorination reactions. Low hydrogen fluoride content PVPHF (3 equivalents of hydrogen fluoride to 1 equivalent of 4-vinylpyridine unit) was also found to be an efficient reagent for bromofluorination of alkenes in the presence of 1,3-dibromo-5,5-dimethylhydantoin. Fluorosulfonic acid-modified PVPHF showed enhanced reactivities for the fluorination of secondary alcohols.

On the solid state of hydrogen fluoride: A self‐consistent crystal field study

AbstractA recently developed self‐consistent crystal field (SCCF) method is applied to two suggested crystal structures of solid hydrogen fluoride, polar and nonpolar, respectively. Constrained geometry optimizations are performed and the results are compared with experiment and previous theoretical studies. Comparisons are also made with a previous SCCF study on hydrogen cyanide. The Pauli repulsion, dispersion, and “classical” crystal field contributions to the lattice energy are calculated. © 1993 John Wiley & Sons, Inc.

Theory of nuclear quadrupole interactions in solid hydrogen fluoride

Theory of nuclear quadrupole interactions in solid hydrogen fluoride

Calculation of the Auger Spectra of Clusters Modelling Solid Hydrogen Fluoride

AbstractThe Auger spectrum of solid hydrogen fluoride is calculated by an ab initio Green's function method. Already small clusters lead to saturation with respect to cluster size. The differences which arise when going from the gas to the solid phase Auger spectrum are mainly a broadening of the lines and the emergence of an additional feature at high kinetic energies. This additional feature is assigned to transitions to delocalized final states.

Ab initio calculations on bent-chain models of solid hydrogen fluoride.

Ab initio Hartree-Fock and Mooslller-Plesset perturbation-theoretical correlation calculations have been performed on a bent hydrogen fluoride chain, modeling solid hydrogen fluoride. It has been found that the lowering of the ionization potential with respect to the monomer is a pure correlation effect, due in considerable part to third-order contributions in the case of the monomer. Finally, the influence of the second-order irreducible vertex part on the exciton binding energies is discussed.

Binding energy analysis of solid hydrogen fluoride

Ab initio energy band structure calculations of infinite single and double HF chains are performed. Interaction energies within and between the linear macromolecules are deduced. As an alternative way for the decomposition of the binding energy tetrameric HF clusters are investigated. Second order perturbation theory is applied to calculate the correlation energy contributions. The interaction of the elementary cell with its neighboring cells in the same layer is repulsive. A binding energy is obtained for the interaction with cells in different layers. The cohesive energy is about - 2 kcal mol -1 with respect to a single HF dimer. The results show that the binding energy in molecular crystals can be determined with the help of molecular cluster calculations.

The Double Minimum Problem Applied to Potassium Hydrogen Fluoride

The doublet character of the infra-red absorption line at 2.67μ of solid potassium hydrogen fluoride is due to the ``tunnel effect.'' The proton has two potential minima between the fluorine nuclei in the FHF− ion. The distance of a minimum to the center of the ion is 0.26A. The height of the potential hill is 33,400 calories.