Metal oxide mixture materials enable the production of dielectric multilayer coatings for highest power laser applications. During thin film deposition, when using sputtering techniques in combination with composite target materials, preferential sputtering occurs on the target surface. The quantitative analysis of the mixture thin film composition, usually performed by ion beam based depth profiling methods, is also affected by preferential sputtering. To gain a deeper understanding, the atomic composition variation of sputtered mixture material surfaces is calculated applying the Monte Carlo simulation program tridyn. The simulation results are compared to the atomic composition gradient measured via depth profiling x-ray photoelectron spectroscopy for mixture thin films composed of HfO2, Sc2O3, Al2O3, and SiO2. The deviations between the experimental and simulated data are discussed with respect to the different mixture material combinations.