The harmonic bonds in our model are soft enough to allow crossing of bonds, unlike the standard bead-spring model of Kremer and Grest. The bond crossing has little effect on the static structure and thermodynamic properties but it significantly affects the relaxation dynamics of polymer chains. The Kremer-Grest model was designed to study reptation dynamics of polymer chains in a melt which required that the crossing of bonds must be avoided. In contrast, our model is designed to study only thermodynamic and structural properties of the systems. Therefore, we allow bond crossing, which accelerates the relaxation dynamics, enabling faster equilibration and more efficient sampling of the simulated systems.