Table 1. Modes, Spectral Activity, Numbering, and Symmetry for an A₂[MHal₆] Material with a Fm3̅m Symmetry, One Formula Unit in the Primitive Cell, the Complex Ion on the O_h Site, and the Counterion on the T_d Site.

			activity
mode	description	symmetry	IR	R	INS
ν1	symmetric M–Hal stretch	A1g	×	√	√
ν2	symmetric M–Hal stretch	Eg	×	√	√
ν3	asymmetric M–Hal stretch	T1u	√	×	√
ν4	asymmetric Hal–M–Hal bend	T1u	√	×	√
ν5	symmetric Hal–M–Hal bend	T2g	×	√	√
ν6	asymmetric Hal–M–Hal bend	T2u	×	×	√
ν7	libration	T1g	×	×	√
ν8	optic translation	T1u	√	×	√
ν9	optic translation	T2g	×	√	√
ν10	acoustic translation	T1u	×	×	√