Can sulfur-containing molecules solvate/ionize HCl? Solid state solvation of HCl on/in methanethiol clusters/nanoparticles.

Solvation of HCl at <100 K at the surface of nanoparticles of methanethiol, a sulfur derivative of methanol, was investigated by FTIR spectroscopy and on-the-fly molecular dynamics as implemented in the density functional code QUICKSTEP (which is part of the CP2K package). Some of the results have been further checked with MP2-level ab initio calculations. Unlike the HCl-CHOH system that has been examined before, HCl on the surface or within methanethiol nanoparticles does not achieve an ionized form.

NH as simple clathrate-hydrate catalyst: Experiment and theory.

The catalytic action of NH within the all-vapor approach for instant clathrate hydrate (CH) formation is studied using both FTIR spectroscopy and ab initio molecular dynamics simulations. A unique property of NH, namely, the rapid abundant penetration and occupation of the water network, creates defects, particularly Bjerrum D-defects, in the hydrate frame that are generally stabilized by guest NH molecules in the cages. Furthermore, insertion of NH seriously disturbs the hydrate network where the guest NH molecules also make fluxional H-bonds with the host water molecules.

A detailed hydrogen bonding analysis on the compositions of HSO/HNO/HO ternary systems: A computational study.

Hydrogen bonding properties of HSO/HNO/HO ternary molecular clusters have been studied by means of structural, energetic, topological, and spectroscopic perspectives. The roles of the hydrogen bonds in the formation of these clusters are considered according to the molecule positions (proton donor or proton acceptor) in the clusters. 33 stable conformers were identified on the potential energy surface.

Hydrogen-bonding behavior of various conformations of the HNO…(CHOH) ternary system.

Nine minima were found on the intermolecular potential energy surface for the ternary system HNO(CHOH) at the MP2/aug-cc-pVDZ level of theory. The cooperative effect, which is a measure of the hydrogen-bonding strength, was probed in these nine conformations of HNO…(CHOH). The results are discussed here in terms of structures, energetics, infrared vibrational frequencies, and topological parameters.

NH as unique non-classical content-former within clathrate hydrates.

High quality FTIR spectra of aerosols of NH-THF and NH-TMO binary clathrate hydrates (CHs) have been measured. Our recently developed all-vapor sub-second approach to clathrate-hydrate formation combined with computational studies has been used to identify vibrational spectroscopic signatures of NH within the gas hydrates. The present study shows that there are three distinct NH types, namely, classical small-cage NH, nonclassical small-cage NH, and NH within the hydrate network.

Molecular Modes and Dynamics of HCl and DCl Guests of Gas Clathrate Hydrates.

Recent years have yielded advances in the placement of unusual molecules as guests within clathrate hydrates (CHs) without severe distortion of the classic lattice structures. Reports describing systems for which observable but limited distortion does occur are available for methanol, ammonia, acetone, and small ether molecules. In these particular examples, the large-cage molecules often participate as non-classical guests H-bonded to the cage walls.

CO2 and C2H2 in cold nanodroplets of oxygenated organic molecules and water.

Recent demonstrations of subsecond and microsecond timescales for formation of clathrate hydrate nanocrystals hint at future methods of control of environmental and industrial gases such as CO2 and methane. Combined results from cold-chamber and supersonic-nozzle [A. S.

Communication: Fourier-transform infrared probing of remarkable quantities of gas trapped in cold homogeneously nucleated nanodroplets.

Studies of catalyzed all-vapor gas-hydrate formation on a sub-second timescale have been extended with a special focus on liquid-droplet compositions at the instant of hydrate crystallization. This focus has been enabled by inclusion of methanol in the all-vapor mixture. This slows droplet to gas-hydrate conversion near 200 K to a time scale suited for standard FTIR sampling.

Tracking all-vapor instant gas-hydrate formation and guest molecule populations: a possible probe for molecules trapped in water nanodroplets.

Quantitative Fourier-transform infrared spectra for low-temperature (160-200 K) aerosols of clathrate-hydrate nanoparticles that contain large-cage catalysts and small-cage nonpolar guests have been extended to a broad range of vapor compositions and sampling conditions. The data better reveal the stages by which room-temperature vapor mixtures, when cooled below ∼220 K, instantly generate aerosols with particles composed exclusively of the corresponding clathrate hydrates. In particular the quantitative data help relate the nature of the hydrates that form to the composition of the aqueous nanodroplets of the first stages of the rapid transition from the all-vapor mixture.

Communication: quantitative Fourier-transform infrared data for competitive loading of small cages during all-vapor instantaneous formation of gas-hydrate aerosols.

A simple method has been developed for the measurement of high quality FTIR spectra of aerosols of gas-hydrate nanoparticles. The application of this method enables quantitative observation of gas hydrates that form on subsecond timescales using our all-vapor approach that includes an ether catalyst rather than high pressures to promote hydrate formation. The sampling method is versatile allowing routine studies at temperatures ranging from 120 to 210 K of either a single gas or the competitive uptake of different gas molecules in small cages of the hydrates.

Proton transfer and autoionization in HNO3·HCl·(H2O)n particles.

The structure and spectroscopic properties of clusters of HNO(3)·HCl·(H(2)O)(n), with n = 1 to 6, have been calculated at the MP2/aug-cc-pVDZ level of theory. Altogether 22 different clusters have been found as stable structures, with minima in their potential energy surfaces. The clusters can be grouped in families with the same number of water molecules, and with close aggregation energies within each family.

Interaction in the ternary complexes of HNO3···HCl···H2O: a theoretical study on energetics, structure, and spectroscopy.

Ternary complexes of HNO(3)···HCl···H(2)O were investigated by ab initio calculations with aug-cc-pVDZ and aug-cc-pVTZ basis sets. The results are analyzed in terms of structures, energetics, and infrared vibrational frequencies. In all minima, neither HNO(3) nor HCl becomes ionized.

Controlling nonclassical content of clathrate hydrates through the choice of molecular guests and temperature.

Low-temperature, low-pressure studies of clathrate hydrates (CHs) have revealed that small ether and other proton-acceptor guests greatly enhance rates of clathrate hydrate nucleation and growth; rapid formation and transformations are enabled at temperatures as low as 110 K, and cool moist vapors containing small ether molecules convert to mixed-gas CHs on a subsecond time scale. More recently, FTIR spectroscopic studies of the tetrahydrofuran (THF)-HCN double clathrate hydrate revealed a sizable frequency shift accompanied by a four-fold intensification of the C-N stretch-mode absorption of the small cage HCN, behavior that is enhanced by cooling and which correlates precisely with similar significant changes of the ether C-O/C-C stretch modes. These temperature-dependent correlated changes in the infrared spectra have been attributed to equilibrated extensive hydrogen bonding of neighboring large- and small-cage guest molecules with water molecules of the intervening wall.

Clathrate hydrates with hydrogen-bonding guests.

Clathrate hydrates (CHs) are inclusion compounds in which "tetrahedrally" bonded H(2)O forms a crystalline host lattice composed of a periodic array of cages. The structure is stabilized by guest particles which occupy the cages and interact with cage walls via van der Waals interactions. A host of atoms or small molecules can act as guests; here the focus is on guests that are capable of strong to intermediate H-bonding to water (small ethers, H(2)S, etc.

Microsolvation of HCl within cold NH3 clusters.

The solid state solvation of HCl molecules with small ammonia clusters at an average temperature of 100 K was investigated by on-the-fly molecular dynamics methodology. Structures close to the proton jump from HCl molecule to the ammonia have been further checked with the MP2/aug-cc-pvDZ calculations. Ionization of HCl and/or sharing of the proton were found.

Interaction in the ternary complexes of HCl-methanol-X, X = H2O or NH3: Ab initio calculations and on-the-fly molecular dynamics.

Dynamics, structures, energetics, and vibrational spectra of the ternary complexes of hydrogen chloride with either methanol and water or methanol and ammonia were investigated by on-the-fly molecular dynamics and ab initio and density functional theory (DFT) with aug-cc-pvDZ basis sets. Addition of CH3OH to the HCl-NH3 system catalyzes the proton transfer from HCl to NH3. However, the dynamics of the system show that the proton is not localized on NH3; rather, it is shared between N and Cl.

Nonadditive effects in the mixed trimers of HCl and methanethiol.

Ab initio and density functional theory calculations with aug-cc-pVDZ and aug-cc-pVTZ basis sets have been performed on the HCl-CH3SH dimer and HCl-(CH3SH)2 and (HCl)2-CH3SH trimers. Structures, energetics, and infrared frequencies are calculated. The results are discussed in terms of the cooperativity effect which is a characteristic of H-bonded systems and compared to oxygen-containing analogs of the same trimers, HCl-(CH3OH)2 and (HCl)2-CH3OH, which have been published recently.

HCl solvation at the surface and within methanol clusters/nanoparticles II: Evidence for molecular wires.

Condensed-phase solvation of HCl on and within methanol nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy, on-the-fly molecular dynamics as implemented in the density functional code Quickstep (which is part of the CP2K package), and ab initio calculations. Adsorption and solvation stages are identified and assigned with the help of calculated infrared spectra obtained from the simulations. The results have been further checked with MP2-level ab initio calculations.