Generalized Born implicit solvent (GBIS) is a fast but approximate method for calculating molecular electrostatics in solvent as described by the Poisson Boltzmann equation which models water as a dielectric continuum. GBIS enables the simulation of atomic structures without including explicit solvent water. The elimination of explicit solvent greatly accelerates simulations; this speedup is lessed by the increased computational complexity of the implicit solvent electrostatic calculation and a longer interaction cutoff. These are discussed in greater detail below.