Polymorphous transformations in alkaline-earth silicates

Structural phase transitions in Ca2SiO4 and Sr2SiO4 are investigated by molecular dynamics simulations. The simulations are based on the potentials calculated from the Gordon–Kim modified electron gas formalism extended to molecular ions. We successfully reproduced the transition γ−αH′−α and β−αL′−αH′−α in Ca2SiO4, and the transition β−α′ in Sr2SiO4. We find that the αL′ phase of Ca2SiO4 is an a×3b×c superstructure of the αH′ phase, while the αH′ phase has a β-K2SO4 structure, and the α phase of Ca2SiO4 has a disordered structure with space group P63/mmc.