  Through extensive molecular simulations we determine a phase diagram of
attractive, flexible polymer chains in two and three dimensions. A surprisingly
rich collection of distinct crystal morphologies appear, which can be finely
tuned through the range of attraction. In three dimensions these include the
face centered cubic, hexagonal close packed, simple hexagonal and body centered
cubic crystals and the Frank-Kasper phase. A simple geometric model is
proposed, based on the concept of cumulative neighbours of ideal crystals,
which can accurately predict most of the observed structures and the
corresponding transitions. The attraction range can thus be considered as an
adjustable parameter for the design of colloidal polymer crystals with tailored
morphologies.
