The incommensurate-commensurate phase transition in akermanite,Ca2MgSi2O7, observed by in-situ 29Si MAS NMR spectroscopy

²⁹Si MAS NMR spectra of synthetic akermanite, Ca₂MgSi₂O₇, exhibit a splitting into three or more lines in the stability feld of the low-temperature incommensurate phase. With increasing temperature, these lines continuously merge into a single line which is then characteristic of the high-temperature, melilite-type structure. The data point to the non-equivalence of Si sites in the low-temperature phase and the gradual structural changes as the phase transition temperature is approached.