  We present second-order molecular cluster perturbation theory (MCPT(2)), a
linear scaling methodology to calculate arbitrarily large systems with explicit
calculation of individual wavefunctions in a coupled-cluster framework. This
new MCPT(2) framework uses coupled-cluster perturbation theory and an expansion
in terms of molecular dimer interactions to obtain molecular wavefunctions that
are infinite-order in both the electronic fluctuation operator and all possible
dimer (and products of dimers) interactions. The MCPT(2) framework has been
implemented in the new SIA/Aces4 parallel architecture, making use of the
advanced dynamic memory control and fine grained parallelism to perform very
large explicit molecular cluster calculations. To illustrate the power of this
method, we have computed energy shifts, lattice site dipole moments, and
harmonic vibrational frequencies via explicit calculation of the bulk system
for the polar and non-polar polymorphs of solid hydrogen fluoride. The explicit
lattice size (without using any periodic boundary conditions) was expanded up
to 1,000 HF molecules, with 32,000 basis functions and 10,000 electrons. Our
obtained HF lattice site dipole moments and harmonic vibrational frequencies
agree well with the existing literature.
