Integral equation study of liquid hydrogen fluoride (original) (raw)
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An improved intermolecular potential function for simulations of liquid hydrogen fluoride
Molecular Physics, 1984
A simple, intermolecular potential function has been derived empirically to yield good thermodynamic and structural results for liquid hydrogen fluoride. The function was tested in Monte Carlo statistical mechanics simulations for the liquid at temperatures of 0°C and -70°C at 1 atm. The average errors in the computed densities and energies are 1 and 5 per cent, respectively. The temperature dependence of the structural results is also analysed by means of radial distribution functions and hydrogen bond distributions. As expected, hydrogen bonded chains dominate the liquid's structure. Enhanced structure and hydrogen bonding are evident as the temperature is lowered. In view of the simplicity of the potential function and the quality of the results, the potential is well suited for simulations of dilute solutions including studies of the solvation of carbonium ions in a model superacid solvent.
Journal of the American Chemical Society, 1978
An intermolecular potential function for the hydrogen fluoride dimer has been determined from ab initio molecular orbital calculations with the extended 6-31G basis set. Interaction energies for 250 configurations of (HF)2 were fit via a statistical procedure to a simple analytic expression that contains 9 adjustable parameters and 16 terms in r-l, r-3, r-6, and r-I2, where r represents internuclear distances. The standard deviations between the 12-6-3-1 potential and the 6-3 1G interaction energies ( A E ) are 0.49 kcal/mol for the 233 points in the range -7.5 < AE < 10 kcal/mol and 0.38 kcal/mol for the 13 1 points with AE < 0. The high quality of the fit and the simplicity of the potential are a great improvement over earlier work in this area. The potential is suitable for use in Monte Carlo simulations of liquid HF and superacid solutions, and in molecular dynamics calculations.
Physical Review B, 1999
We present an attempt to build up a new two-body effective potential for hydrogen fluoride, fitted to theoretical and experimental data relevant not only to the gas and liquid phases, but also to the crystal. The model is simple enough to be used in Molecular Dynamics and Monte Carlo simulations. The potential consists of: a) an intra-molecular contribution, allowing for variations of the molecular length, plus b) an inter-molecular part, with three charged sites on each monomer and a Buckingham "exp−6" interaction between fluorines. The model is able to reproduce a significant number of observables on the monomer, dimer, hexamer, solid and liquid forms of HF. The shortcomings of the model are pointed out and possible improvements are finally discussed. 31.15.Qg, 61.25.Em, 34.20.Cf
J Phys Chem B, 2003
We applied a Quantum Mechanics/Molecular Mechanics method (QM/MM) that makes use of the mean field approximation to study the polarization of hydrogen fluoride (HF) in its liquid phase. The method is based on the calculation of the Averaged Solvent Electrostatic Potential from Molecular Dynamics data (ASEP/ MD). Our model considers the HF molecule to be nonrigid, the H-F bond length can vary, and includes the effect of the electron correlation calculated at the Møller-Plesset second-order (MP2) level and the effect of the solvent polarization. The H-F bond elongates and undergoes strong polarization when it passes from the gas to the liquid phase. The ASEP/MD method provides an adequate description of this polarization, and reproduces adequately both the thermodynamics and the structure of the liquid. A comparison between the performances of two-site and three-site models for the HF molecule is also presented.
Chemical Physics Letters, 2010
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New Molecular-Mechanics Model for Simulations of Hydrogen Fluoride in Chemistry and Biology
Journal of Chemical Theory and Computation, 2020
Hydrogen fluoride (HF) is the most polar diatomic molecule and one of the simplest molecules capable of hydrogen-bonding. HF deviates from ideality both in the gas phase and in solution, and is thus of great interest from a fundamental standpoint. Pure and aqueous HF solutions are also broadly used in chemical and industrial processes, despite their high toxicity. HF is a stable species also in some biological conditions, because it does not readily dissociate in water unlike other hydrogen halides; yet, little is known about how HF interacts with biomolecules. Here, we set out to develop a molecular-mechanics model to enable computer simulations of HF in chemical and biological applications. This model is based on a comprehensive high-level ab initio quantum chemical investigation of the structure and energetics of the HF monomer and dimer; (HF) n clusters, for n = 3-7; various clusters of HF and H 2 O; and complexes of HF with analogs of all 20 amino-acids and of several commonly occurring lipids, both neutral and ionized. This systematic analysis explains the unique properties of this molecule; for example, that interacting HF molecules favor non-linear geometries despite being diatomic, and that HF is a strong H-bond donor but a poor acceptor. The ab initio data also enables us to calibrate a three-site molecular mechanics model, with which we investigate the structure and thermodynamic properties of gaseous, liquid, and supercritical HF in a wide range of temperatures and pressures; the solvation structure of HF in water and of H 2 O in liquid HF; and the free diffusion of HF across a lipid bilayer, a key process underlying the high cytotoxicity of HF. Despite its inherent simplifications, the model presented significantly improves upon previous efforts to capture the properties of pure and aqueous HF fluids by molecular-mechanics methods, and to our knowledge constitutes the first parameter set calibrated for biomolecular simulations.
Structural and microscopic relaxation processes in liquid hydrogen fluoride
2002
The high frequency collective dynamics of liquid hydrogen fluoride is studied by inelastic x-ray scattering on the coexistence curve at T 239 K. The comparison with existing molecular dynamics simulations shows the existence of two active relaxation processes with characteristic time scales in the subpicosecond range. The observed scenario is very similar to that found in liquid water. This suggests that hydrogen bonded liquids behave similarly to other very different systems as simple and glass forming liquids, thus indicating that these two relaxation processes are universal features of the liquid state.
Transport properties of liquid hydrogen fluoride
The Journal of Chemical Physics, 2000
The dynamical properties of liquid hydrogen fluoride are investigated by a molecular dynamics study of the correlation functions relevant for a generalized hydrodynamics description of transport coefficients. The results are compared with the corresponding ones in liquid water in order to understand the role of hydrogen bonding in the two systems. The different behavior can ultimately be attributed to the arrangement of the molecules, which form irregular chains in HF and a tetrahedral network in water. For the two systems, the differences between experimentally measurable quantities are also pointed out and discussed.
Ab initio molecular dynamics simulation of liquid hydrogen fluoride
The Journal of Chemical Physics, 1997
First-principles molecular dynamics simulations are carried out to study the structures, dynamics, and electronic properties of liquid Al 88 Si 12 in the temperature ranging from 898 to 1298 K. The temperature dependence of static structure factors, pair correlation functions, and electronic density-of-states are investigated. The structural properties obtained from the simulations are in good agreement with the x-ray diffraction experimental results.
A model intermolecular potential for hydrogen fluoride including polarizability
Chemical Physics Letters, 1986
An intermolecular potential model for hydrogen fluoride is proposed. This has a central Lennard-Jones part, three axial charges fixed by the dipole and quadrupole moments, and anisotropic polarizability. Good agreement with experimental values is found for the dimer, liquid and crystal lattice structures and energies, and for the second virial coefficient.