Table II:

Unstable LO and TO phonon frequencies and mode effective charges in SrNb₆O₁₆ at Γ. The first two columns are the frequency in cm⁻¹ and the mode Born effective charge of the LO modes, the second two columns are the same but for the TO modes. There is one anti-polar mode with zero mode effective charge that is unaffected by electrostatic boundary conditions.

Mode Number	LO Freq. cm−1	LO Mode Z*	TO Freq. cm−1	TO Mode Z*
1	176i	21.8	139i	0.23
2	138i	5.9	128i	0
3	128i	0	85i	1.2
4	44i	10.2	29i	0.32