  We present a coarse-grained model of DNA-functionalized colloids that is
computationally tractable. Importantly, the model parameters are solely based
on experimental data. Using this highly simplified model, we can predict the
phase behavior of DNA-functionalized nano-colloids without assuming pairwise
additivity of the inter-colloidal interactions. Our simulations show that for
nano-colloids, the assumption of pairwise additivity leads to substantial
errors in the estimate of the free energy of the crystal phase. We compare our
results with available experimental data and find that the simulations predict
the correct structure of the solid phase and yield a very good estimate of the
melting temperature. Current experimental estimates for the contour length and
persistence length of single-stranded DNA sequences are subject to relatively
large uncertainties. Using the best available estimates, we obtain predictions
for the crystal lattice constants that are off by a few percent: this indicates
that more accurate experimental data on ssDNA are needed to exploit the full
power of our coarse-grained approach.
