  We explore the potential energy surfaces for NH molecules interacting with
alkali-metal and alkaline-earth atoms using highly correlated ab-initio
electronic structure calculations. The surfaces for interaction with
alkali-metal atoms have deep wells dominated by covalent forces. The resulting
strong anisotropies will produce strongly inelastic collisions. The surfaces
for interaction with alkaline-earth atoms have shallower wells that are
dominated by induction and dispersion forces. For Be and Mg the anisotropy is
small compared to the rotational constant of NH, so that collisions will be
relatively weakly inelastic. Be and Mg are thus promising coolants for
sympathetic cooling of NH to the ultracold regime.
