Table 1 On-site couplings between ferroelectric soft mode P and high-frequency auxiliary mode Q.

2.02 × 10¹³

\({{{\Lambda }}}_{2}({P}_{x}^{2}{Q}_{x}^{2}+{P}_{y}^{2}{Q}_{y}^{2}+{P}_{z}^{2}{Q}_{z}^{2})\)

−2.13 × 10¹²

\({{{\Lambda }}}_{22}({P}_{x}^{2}{Q}_{y}^{2}+{P}_{x}^{2}{Q}_{z}^{2}+{P}_{y}^{2}{Q}_{z}^{2}+{P}_{y}^{2}{Q}_{x}^{2}+{P}_{z}^{2}{Q}_{x}^{2}+{P}_{z}^{2}{Q}_{y}^{2})\)

2.68 × 10¹¹

\({{{\Lambda }}}_{3}({P}_{x}^{3}{Q}_{x}+{P}_{y}^{3}{Q}_{y}+{P}_{z}^{3}{Q}_{z})\)

8.86 × 10¹¹

\({{{\Lambda }}}_{1}({P}_{x}{Q}_{x}^{3}+{P}_{y}{Q}_{y}^{3}+{P}_{z}{Q}_{z}^{3})\)

9.69 × 10¹¹

\({{{\Lambda }}}_{211}({P}_{x}^{2}{P}_{y}{Q}_{y}+{P}_{x}{P}_{y}^{2}{Q}_{x}+{P}_{x}^{2}{P}_{z}{Q}_{z}+{P}_{x}{P}_{z}^{2}{Q}_{x}+{P}_{y}^{2}{P}_{z}{Q}_{z}+{P}_{y}{P}_{z}^{2}{Q}_{y})\)

−4.61 × 10¹¹

\({{{\Lambda }}}_{112}({P}_{x}{Q}_{x}{Q}_{y}^{2}+{P}_{y}{Q}_{x}^{2}{Q}_{y}+{P}_{z}{Q}_{x}^{2}{Q}_{z}+{P}_{x}{Q}_{x}{Q}_{z}^{2}+{P}_{z}{Q}_{y}^{2}{Q}_{z}+{P}_{y}{Q}_{y}{Q}_{z}^{2})\)

1.70 × 10¹³

Λ₁₁₁₁(P_xP_yQ_xQ_y + P_yP_zQ_yQ_z + P_zP_xQ_zQ_x)