Table V.

Root-mean-square fluctuations σ(μ) of the ${\text{t}}_{1\text{u}}^{(1)}$ modes of PbTiO3 as a function of temperature, as computed by ab initio molecular dynamics. Quantities in parentheses indicate one standard deviation uncertainty as calculated from five time averages. To convert into atomic displacements, multiply by the displacement patterns described in Table I. Root-mean-square fluctuations for the other modes as a function of temperature can be found in Table S2 of the Supplemental Material[19].

Mode μ	σ(μ)
	300 K	600 K	900 K
${\text{t}}_{1\text{u}}^{(1)}(x;y)$	0.0138(1)	0.0207(4)	0.0294(3)
${\text{t}}_{1\text{u}}^{(1)}(z)$	0.0592(1)	0.0495(4)	0.0294(3)