The all-atom CHARMM36 (C36) force field is used to simulate bilayers of pure palmitoylsphingomyelin (PSM) as well as binary Mixtures of PSM and steatoyl-sphingomyelin (SSM) at various cholesterol concentrations (X-c) and temperatures. C36 simulation data is in good agreement with experimental deuterium order parameters and previous computational results, providing evidonce of the utility of the force field for potentially studying more complex membranes. The area compressibility modulus is shown to achieve a large value of 2.82 +/- 0.08 N/m in cholesterol-rich membranes (X-c = 0.50). Surface area per lipid (SA/lip) tilt angle, membrane thicknesses, and aryl chain ordering are shown to have strong dependencies on cholesterol concentration. Relaxation times also indicate cholesterol,dependence and show a strong preference for rotational axial motion over wobbling motion: Radial distribution functions and lipid clustering-indicate strong, relationships between lateral,ordering and-hydrogen = bonding, which is long lived in SM membranes. These interactions lead to strong self-association of cholesterol at high concentrations, causing shielding from further SM-cholesterol interactions. The importance of a ternary component on SM SM hydrogen bonds is revealed in light of previous results and is consequential in the modeling of