Crystal structures of some cubic hexafluorophosphates at ambient temperatures

Structures of some alkaline metals and silver(I) hexafluorophosphates, MPF6, have been determined by X-ray single crystallography at ambient temperatures. Although all the salts exhibit a rock salt structure (Fm3̄m), three types arise due to the orientational disorders of anions. In NaPF6, Na+ and octahedral PF6− form a linear P–F–Na array without a disorder. PF6− in AgPF6 shows a three-fold orientational disorder described as a rotation by 45° around one of the three crystal axes starting from the original position found in NaPF6. Salts of the heavier alkaline metals are isostructural, showing a four-fold orientational disorder of PF6− described as a rotation by 60° around one of the four diagonals of the crystal lattice from the original orientation in NaPF6.