The perovskite-structured phases and their associated phase transitions remain an enduring topic of study within the solid state sciences due to their importance in both applied science (non-volatile ferroelectric random access memories being a major money spinner), and pure science (all elements except the noble gases are claimed to occur within a perovskite structure) as they exhibit a wide ranging spectrum of physical properties. In this proposal we aim to satisfy interests ranging from physics (applying thermodynamical models to crystallographic changes) to geophysics (studying analogue phases of the most common mineral in the Earth's lower mantle). We propose to study changes in the crystal structure of potassium manganese fluoride as a function of temperature and pressure to assist in geophysical modelling of the lower mantle.