Chemical Bonding Effects and Physical Properties of Noncentrosymmetric Hexagonal Fluorocarbonates ABCOF (A: K, Rb, Cs; B: Mg, Ca, Sr, Zn, Cd).

The present work applied the methods of density functional theory and the van der Waals interaction PBE + D3(BJ) on the basis of localized orbitals of the CRYSTAL17 package. It featured the effect of interactions between structural elements of fluorocarbonates ABCOF (A: K, Rb, Cs; B: Mg, Ca, Sr, Zn, Cd) on their elastic and vibrational properties. The hexagonal structures proved to consist of alternating ···B-CO··· and ···A-F··· layers in planes , interconnected along axis by infinite chains ···F-B-F···, where cations formed polyhedra AOF and BOF.

Deep Functional Profiling of Wild Animal Microbiomes Reveals Probiotic Strains with a Common Biosynthetic Fingerprint.

The biodiversity of microorganisms is maintained by intricate nets of interactions between competing species. Impaired functionality of human microbiomes correlates with their reduced biodiversity originating from aseptic environmental conditions and antibiotic use. Microbiomes of wild animals are free of these selective pressures.

First-Principle Studies of the Vibrational Properties of Carbonates under Pressure.

Using the density functional theory with the hybrid functional B3LYP and the basis of localized orbitals of the CRYSTAL17 program code, the dependences of the wavenumbers of normal long-wave vibrations on the (GPa) pressure (cm) = + (/)· + (/)· and structural parameters (Å) (: , , , , ): (cm) = + (/) - ( - ) were calculated. Calculations were made for crystals with the structure of calcite (MgCO, ZnCO, CdCO), dolomite (CaMg(CO), CdMg(CO), CaZn(CO)) and aragonite (SrCO, BaCO, PbCO). A comparison with the experimental data showed that the derivatives can be used to determine the pressures, , , lattice constants and the metal-oxygen, and the carbon-oxygen interatomic distances from the known Δ shifts.

Comprehensive Density Functional Theory Studies of Vibrational Spectra of Carbonates.

Within the framework of the density functional theory (DFT) and the hybrid functional B3LYP by means of the CRYSTAL17 program code, the wavenumbers and intensities of normal oscillations of MgCO, CaCO, ZnCO, CdCO in the structure of calcite; CaMg(CO), CdMg(CO), CaMn(CO), CaZn(CO) in the structure of dolomite; BaMg(CO) in the structure of the norsethite type; and CaCO, SrCO, BaCO, and PbCO in the structure of aragonite were calculated. Infrared absorption and Raman spectra were compared with the known experimental data of synthetic and natural crystals. For lattice and intramolecular modes, linear dependences on the radius and mass of the metal cation are established.

Semi-empirical and calculations for crystals under pressure at fixed temperatures: the case of guanidinium perchlorate.

A simple semi-empirical approach is proposed to calculate structure and properties of crystals under pressure at fixed temperatures. The computed semi-empirical pressure dependencies for guanidinium perchlorate are in good agreement with available experimental data. results within quasi-harmonic approximation for guanidinium perchlorate are also presented.