for a full hydrodynamic calculation.

This code is based on the following model for the formation of binary stellar systems (Figure \[bate.model\]). The model begins with a molecular cloud core of known initial density and angular momentum profile. It is assumed that this cloud begins to collapse and that a ‘seed’ binary system is formed at the centre, presumably via some sort of fragmentation. The ‘seed’ binary has mass ratio $q \leq 1$, separation $a$, and is assumed to have a circular orbit. It initial consists of only a small fraction of the total mass of the core and is assumed to have formed from the gas that was originally contained within a sphere of radius $r$, at the centre of the initial cloud (Figure \[bate.model\]). For the results presented in this proceedings, the separation of the ‘seed’ binary is set by assuming that the angular momentum of the gas from which the binary forms is equal to the orbital angular momentum of the binary.

Subsequently, the binary accretes the remainder of the initial cloud (which falls on to the binary) and the binary’s properties evolve due to the accretion. This evolution is calculated by taking a thin shell of 