Line ratios (in phot cm⁻² s⁻¹) for key diagnostics lines of Ca XIV as a function of density at a fixed temperature of 3.55 × 10⁶ K (the peak ion abundance in ionisation equilibrium). The solid curve is calculated with the present R-matrix data, while the dashed curve use distorted wave data as incorporated in CHIANTI version 3. The square indicates the measurement from a post-flare solar SUMER observation (Landi et al. 2003).