Stability of O3 + N2, O3 + O2 and O3 + CO2 double hydrates: DFT study

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Calculations of van der Waals interaction energies for Al, Cr, Fe, and Ir acetylacetonate crystals

Experimental data have been analyzed and interpreted for four volatile acetylacetonates of trivalent metals Al, Cr, Fe, and Ir. The crystal lattice energies were calculated by the atom-atom potential method. The lattice energies obtained by using the Buckingham potential are in better agreement with the sublimation heats of these metal complexes than those calculated from the Lennard-Jones potential. The experimental dependences of vapor pressure for the complexes are in satisfactory agreement with the values obtained from the calculated lattice energies and entropies of crystal-gas transitions.     

Theoretical Study of Clathrate Hydrates with Multiple Occupation

In this work, the electronic, structural, dynamic andthermodynamic properties of structure II, H and tetragonalAr clathrate hydrates have been calculated and the effectof multiple occupancy on their stability has been examinedusing first-principles and lattice dynamics calculations.The dynamic properties of these clathrates have beeninvestigated depending on the number of guest moleculesin a clathrate cage. It has been found that selectedhydrate structures are dynamically stable. The calculatedcell parameters are in agreement with experimental data.We also report the results of a systematic investigationof cage-like water structures using first-principles calculations. Ithas been observed that Ar clusters can be stabilized indifferent water cages and the stability is strongly dependenton the number of argon atoms inside the cages.     

Relationship between the Dynamic Properties of 1h Ice and Xenon Hydrate and the Interplay of Intramolecular and Intermolecular Vibrations

A new approach was used to simulate vibration spectra of 1h ice and xenon hydrate in the range 0–4000 cm^-1, which encompasses both intramolecular and intermolecular vibrations. This approach, based on the lattice dynamics method, enables full spectra to be obtained for molecular crystals with allowance for the coupling of intramolecular and lattice vibrations. It is shown that consideration of this coupling leads to splitting of the peaks of intramolecular vibrations and to a significant change in the spectrum in the range of translation and libration molecular vibrations, which agrees qualitatively with experimental results.     

Thermodynamic discontinuity between low-density amorphous ice and supercooled water

A combination of reverse Monte Carlo, molecular dynamics, and lattice dynamics simulations were used to obtain structural and thermodynamic data for low-density amorphous ice. A thermodynamically discontinuous transformation to a phase with properties and a structure consistent with supercooled liquid water is found to occur at approximately 130 K. Quantum corrections have a profound effect on thermodynamic properties and the location of important thermodynamic points in the water phase diagram.     

Some polishing experiments on copper in a hyperbolic cell

Some polishing experiments have been carried out on copper anodes in a hyperbolic cell designed by Gilmont and Walton, using orthophosphoric acid as the electrolyte. The results obtained have been compared to those obtained in similar experiments in a Hull cell. It has been found that very similar bands of different reflectivity and polishes are found to form in both the cells. These bands shift with time and a study of such displacements has been made. The results are briefly discussed.     

Dynamic and thermodynamic properties of clathrate hydrates

Vibrational spectra and thermodynamic properties of ices and the cubic structure I (CS-I) clathrate hydrate have been studied by the lattice dynamics method. The phonon density of states for the empty hydrate framework and for xenon hydrate have been determined; the vibrational frequencies of the guest molecules in large and small cavities have been found. The stability of the hydrate with respect to the external pressure at low temperatures and its thermodynamic stability at temperatures around 0°C have been studied. It has been found that the empty hydrate framework is unstable in certain temperature and pressure regions. A definite degree of occupation of the large cavities by the guest molecules is necessary for the hydrate to become stable. It has been found that there is a maximum of the critical temperature at which the hydrate exists, which is a function of the external pressure.Dedicated to Dr. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

Modular,Homochiral, Porous Coordination Polymers: Rational Design,Enantioselective Guest Exchange Sorption and Ab Initio Calculations of Host–Guest Interactions

Two new, homochiral, porous metal–organic coordination polymers [Zn₂(ndc){(R)‐man}(dmf)]?3DMF and [Zn₂(bpdc){(R)‐man}(dmf)]?2DMF (ndc=2,6‐naphthalenedicarboxylate; bpdc=4,4′‐biphenyldicarboxylate; man=mandelate; dmf=N,N′‐dimethylformamide) have been synthesized by heating Zn^II nitrate, H₂ndc or H₂bpdc and chiral (R)‐mandelic acid (H₂man) in DMF. The colorless crystals were obtained and their structures were established by single‐crystal X‐ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn₂(bdc){(S)‐lac}(dmf)]?DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal–organic frameworks effectively and stereoselectively (ee up to 62 %) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn₂(bdc){(S)‐lac}(dmf)]?DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH₃SO(CH₂)₄OH. The new homochiral porous metal–organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2‐NaphSMe (2‐C₁₀H₇SMe) and PhSCH₂Ph) that could not be achieved by the smaller‐pore [Zn₂(bdc){(S)‐lac}(dmf)]?DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn₂(bdc){(S)‐lac}(dmf)]?DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo‐preference is accounted for by the presence of coordinated inner‐pore DMF molecule that forms a weak C? H???O bond between the DMF methyl group and the (S)‐PhSOCH₃ sulfinyl group.