Ordering of monomers, dimers and polymers of deposited BrIPy molecules: a modeling study.

We propose a lattice model describing the ordering of 1,6-dibromo-3,8-diiodopyrene (BrIPy) molecules on the Au(111) surface into two-dimensional structures and correlated one dimensional rows. Our model employs three (intact, singly and doubly deiodinated) types of BrIPy molecules and mimics the situation which occurs with increasing temperature, where the majority of intact molecules form ordered two-dimensional networks, while most of the doubly deiodinated molecules assemble into long organometallic polymeric rows. We use DFT calculations to determine the values of intermolecular interactions for intact molecules and propose a strategy for estimating the interactions for deiodinated molecules, where the organometallic interaction with Au atoms plays the dominant role.

Exploring the Antipolar Nature of Methylammonium Lead Halides: A Monte Carlo and Pyrocurrent Study.

The high power conversion efficiency of the hybrid CHNHPbX (where X = I, Br, Cl) solar cells is believed to be tightly related to the dynamics and arrangement of the methylammonium cations. In this Letter, we propose a statistical phase transition model which accurately describes the ordering of the CHNH cations and the whole phase transition sequence of the CHNHPbI perovskite. The model is based on the available structural information and involves the short-range strain-mediated and long-range dipolar interactions between the cations.

Structural phase transition in perovskite metal-formate frameworks: a Potts-type model with dipolar interactions.

We propose a combined experimental and numerical study to describe an order-disorder structural phase transition in perovskite-based [(CH3)2NH2][M(HCOO)3] (M = Zn(2+), Mn(2+), Fe(2+), Co(2+) and Ni(2+)) dense metal-organic frameworks (MOFs). The three-fold degenerate orientation of the molecular (CH3)2NH2(+) (DMA(+)) cation implies a selection of the statistical three-state model of the Potts type. It is constructed on a simple cubic lattice where each lattice point can be occupied by a DMA(+) cation in one of the available states.