The interactions between all atoms, and therefore the potential energy, must be accurately described in order to predict CO2 and N2 adsorption in MOFs. In classical GCMC, this is typically achieved by defining an appropriate set of equations and molecular parameters known as a forcefield (FF), whereby short-range repulsion / dispersion interactions are described by a Lennard-Jones (LJ) potential, and long-range electrostatic interactions by a Coulombic potential. Specialised FFs have been developed to accurately describe the LJ contributions in specific subclasses of MOFs, however these lack the large-scale predictive capabilities needed for screening purposes. On the other hand, generic FFs such as Dreiding and the Universal Force Field (UFF) are transferable (albeit less accurate) as they describe the same types of framework atoms in many different materials with the same parameters. Therefore, Dreiding or UFF are the common and practical choices for HTCS of MOFs. They are typically combined with the Transferable Potentials for Phase Equilibria (TraPPE) FF (which describes the CO2 and N2 adsorbates) using mixing rules such as Lorentz-Berthelot. For the electrostatic interactions, partial charges must be assigned to each atom in the system. Several assignment schemes have been developed so far and have been reviewed elsewhere, each differing in their level of accuracy, philosophy, and computational cost. The most accurate (but computationally expensive) approach would be to determine the electrostatic potential within a material using ab initio calculations and then assign point charges that best represents this electronic environment. While many ab initio approaches exist, density derived electrostatic and chemical (DDEC) charges and Repeating Electrostatic Potential Extracted ATomic (REPEAT) charges are considered to be the best options for periodic structures. Less accurate, but computationally inexpensive, charges can also be obtained using charge equilibration (Qeq) schemes such as the Extended Qeq (EQeq) and Periodic Qeq (PQeq) methods, among others. These approaches are based on the principle of electronegativity equalisation between bonded atoms, and have been used extensively in MOF screening studies despite their semiempirical nature. Despite the consensus that ab initio charges are the preferred choice for HTCS, several practical considerations (such as the availability of computational resources) can motivate the choice of charge equilibration schemes. Additionally, it is currently nontrivial to obtain a set of LJ parameters capable of screening thousands of MOFs with high accuracy.