Vol 468, No 1 (2016)

Due to the large size of light-harvesting complexes, approximate methods are commonly used for calculating the coupling energies between their constituents. Two approximate methods are studied in this work: TrESP and the recently suggested TrCAMM method, based on the expansion of the one-particle density matrix. The quality of approximation of the electrostatic potential in the framework of these two approaches has been compared for two biological pigments as an example—chlorophyll a and bacteriochlorophyll a. It has been shown that both approaches provide high accuracy of approximation of the matrix elements of the electrostatic potential operator. In addition, it has been demonstrated that symmetrization of the one-particle density matrix in the framework of the TrCAMM method significantly improves the calculation accuracy and makes the computational procedure unambiguous.

Previously unknown cationic platinum complexes Pt(C₅H₄N)(C₅H₅N)⁺ and Pt(C₅H₄N)⁺, where platinum atom forms an unusual three-membered metallacycle with a deprotonated pyridine molecule, were detected in the gas phase by mass spectrometry and structurally characterized by DFT quantum-chemical calculations.

The solubility of oxygen in liquid nickel containing zirconium at 1873 K has been experimentally studied for the first time. It has been shown that zirconium is a rather strong deoxidizing agent in liquid nickel. The equilibrium constant of the reaction of zirconium and oxygen dissolved in liquid nickel (logK_(1)(Ni) =–6.788), the interaction parameters characterizing these solutions (e_Zr(Ni)^O =–2.01; e_O(Ni)^Zr =–0.35; e_Zr(Ni)^Zr = 0.24), and the activity coefficient of zirconium in nickel at infinite dilution (γ_Zr(Ni)^o = 1.03 × 10^–8) have been determined. The zirconium content at the minimum of the oxygen solubility curve and the corresponding oxygen concentration have been determined.