“…However, due to the lack of single-crystal X-ray diffraction data, this model was calibrated only on the basis of structural data and site occupancies on armalcolite reported by Smyth (8) and Wechsler (3). Despite the sophistication of the model proposed by Brown and Navrotsky (12), caution should be exercised when it is applied to the end members, because of the difficulty in accurately determining site occupancies of three cations (Fe, Mg, and Ti) between two sites in Fe Mg Ti O (3,7,8,11). We have undertaken a singlecrystal X-ray diffraction study on five synthetic MgTi O crystals annealed at 600, 700, 800, 1000, and 1400°C to characterize variations of the unit-cell parameters and crystal structure of MgTi O with cation order-disorder.…”