Top: comparison of the X-Shooter optical and near-infrared spectra (black line) of the L (left) and T (right) components of Luhman 16AB and the BT-Settl model atmosphere with 1400/5.0 (red line) and normalised around 800 nm to match the potassium wings. Bottom: same X-Shooter spectra (black line) compared to synthetic spectra generated combining the WITA chemical code with the BT-Settl model atmosphere for a temperature of 1400 K, a gravity of log  (g) of 5.0−5.5, and different relative abundances of Na, K, and other refractory elements (smoothed for visualisation purposes).