tokens: the inner initial region of the debris disc is chosen as to coincide with the appropriate tidal radius given the NS and WD properties. However, the exact structure of the debris disc is more complex than our simplified models and we therefore checked the dependence of slightly by moving the disc position inwards or outwards (see R 0 / r t in Table 2 ). As we show, the results depend on the chosen inner positions, but the overall behaviour is robust and is not strongly dependent on the exact choice. Closer-in debris discs are more effective in allowing for material to accrete into close-in orbits before outflows become efficient enough to quench further accretion. The overall ejected mass and total energetic are therefore determined by both the overall NS and WD mass and the inner radius of the disc; these are well reflected in Table 2 . Overall the nuclear energy deposited increases with increasing density and with Helium content. These provide more favourable conditions for nuclear burning. The density is determined by the total mass of the debris disc (the disrupted WD), the inner radius ( r d ), the disc scale height, and to some extent the disc composition that affects the EOS (see equation 3 ). As can be seen in Table 2 , the nuclear energy produced follows these various trends; it increases with increasing WD mass and Helium content, as well as with decreasing disc scale height and inner radius. The tidal radius, which determines the inner radius, depends on both the NS mass and the WD mass, as well as on the WD composition, and hence more massive NSs (giving rise to larger tidal radii) correspond to lesser production of nuclear energy. The pure Helium WD case (not shown) is the only case where no nuclear burning is observed. This may appear counter-intuitive given the lower temperatures and densities required to ignite Helium, however such WDs have a lower mass and are much puffier, hence the effective density of the debris disc they produce is far lower than that of CO WD debris disc, explaining the result. As discussed above, our results suggest that only a small fraction of the WD debris disc is effectively ejected during the modelled evolution, while most of the material expands to produce a more isotropic configuration, but stays bound to the NS. The long-term evolution of such expanded debris ‘atmosphere’ is beyond the scope (and computational capabilities) of the current study focusing on the immediate outcomes of the merger following the disruption of the WD. As already noted, nuclear burning is not the main driver of the outflows in NS–WD mergers, and only a small fraction of the WD debris disc experiences any nuclear burning. Hence, the majority of the ejected unbound material (identified through the comparison of the kinetic and potential energy of each mass element) shows the same composition as the original WD, i.e. C/O composition (and He in the hybrid WD cases). However, most of the unbound material is ejected through
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