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For the last few years technical improvements of compositions and preparation procedures for perovskite-based solar cells have remarkably enhanced their energy conversion efficiency. Crystal and electronic structures together with ion diffusion in partially substituted cubic methylammonium (MA) perovskite based on lead halide MA0.5X0.5PbI3, where X is the cation, are theoretically investigated using density functional theory and molecular dynamics methods. The electronic structure of partially substituted perovskites studied is similar to the MAPbI3 structure, however, the band gap changes compared to their structures. Partial MA substitution distorts the lattice, which prevents MA or X diffusion between A sites in the perovskite crystal. The partial cation substitution affects the electronic structure and distorts the crystal lattice of perovskite, which makes it possible to control the optical properties of the material in different spectral regions and to influence the electronic composition of defects. [ABSTRACT FROM AUTHOR]

QSPR-modeling of melting temperatures has been performed for oligophenylenes of diverse structures and different molecular weights. It has been shown that optimization of correlation weights of graph local invariants can be used for prediction of melting points of oligomers. The best statistical quality of the model is observed for correlation weights calculated using third-order Morgan degrees. [ABSTRACT FROM AUTHOR]

Prediction of the vitrification temperatures of polyarylene oxides based on optimization of the local invariant correlation weights of molecular graphs for the test sample is statistically characterized byn= 18,r= 0.9288,s= 12.8°C,F= 100. [ABSTRACT FROM AUTHOR]