First-principles study of organically modified muscovite mica with ammonium ion

Using density functional theory calculations, we have investigated the interlayer cation exchange phenomena in muscovite mica, which is motivated by a necessity to develop flexible high-insulating covering materials. The crystalline structures, chemical bonding properties, energetics, and electronic properties of muscovites before and after exchange of interlayer K.sup.+ cation with ammonium (NH [Formula omitted]) or methylammonium (CH.sub.3NH ) ion were calculated. It was found that the unit cell volume changes are negligibly small upon exchange with NH ion, while the unit cells are expanded with about 4 % relative rate when replacing the interlayer K.sup.+ cation with CH.sub.3NH ion. The energy band gap of pre-exchanged muscovite was calculated to be about 5 eV, which hardly changes upon interlayer cation exchange with either NH or CH.sub.3NH ion, indicating the preservation of high insulating property of muscovite. The exchange energies were found to be about -100 kJ/mol for NH and about -50 kJ/mol for CH.sub.3NH exchange, indicating that the exchange reactions are exothermic. A detailed analysis of atomic resolved density of states and electron density redistribution was provided.