Order-disorder phase transitions in KNO2, CsNO2, and TlNO2 crystals: A molecular dynamics study - art. no. 144105

The order-disorder phase transitions of KNO2, CsNO2, and TINO2 have been st udied using parameter-free molecular dynamics simulation. It is found that the phase transitions in nitrites investigated are driven by the rotations of the NO2- ions about different axes together with displacements of cation s and anions. We successfully reproduce the high-temperature phases of thes e nitrites. i.e., the NaCl-like structure for KNO2 and CsCl-like structure for Cs(Tl)NO2. Based on the investigation of the radial distribution functi on of the cations and anions, we explain why KNO2 and Cs(Tl)NO2 form quite different low-temperature phases.