Comparison of best-fitting models (blue) for observed spectra (black) of HD 13854 and HD 14956 (upper and lower lines in each sub-panel). The three rows show lines of different ionisation stages of silicon: Si II λλ4128 and 4130 Å (upper left), Si II λλ6347 and 6371 Å (upper right); the Si III triplet λ4552–4575 Å and Si III 15739 Å (middle left), Si III λλ5473 and 5540 Å (middle right); Si IV λλ4088 and 4116 Å (lower left), Si IV λλ4212 and 4666 Å (lower right panel).