Simulations to parameterize molecular-mechanical force fields were performed using GRO-MACS 5.1.4. The simulations were performed under periodic boundary conditions with unit cells containing 1000 molecules. Where possible, initial coordinates were taken from the Virtual Chemistry database. In the remaining cases, initial coordinates were generated using the GROMACS insert-molecules module. A Parrinello-Rahman barostat and Nosé-Hoover thermostat were used in order to sample the isothermal-isobaric ensembles. Electrostatic interactions were calculated using Particle Mesh Ewald (PME) with a grid spacing of 1 Å. Lennard-Jones interactions were calculated using the lattice-sum method. Properties were calculated from a 1 ns simulation to equilibrate the system followed by a 1 ns simulation to sample the properties. Sample input files are included in Supporting Information.