Passive radiation detectors based on the optically stimulated luminescence of anion-defective aluminum-oxide doped with carbon (Al2O3:C) are commonly used for personal, environment and medical dosimetry. However, their luminescence efficiency in measuring a certain type of radiation is strongly affected by the pattern of energy deposition at the nanoscale and the corresponding possible saturation of trapping, luminescent or competitive centers within the detector. To better understand the results of the measurements and to further exploit their use in complex radiation environments, including space and clinical particle beams, the efficiency of the detectors should be known for a wide variety of particles and particle energies. In this work, radiation transport simulations using the Monte Carlo code PHITS are coupled with the Microdosimetric d(z) Model to calculate the efficiency of the blue emission (F centers) of Al2O3:C (Luxel) optically stimulated luminescent detectors in case of exposures to ions from 1H to 132Xe. The model was initially developed to describe the response of differently doped thermoluminescent detectors based on lithium fluoride. This study represents the first application of the Microdosimetric d(z) Model to a different material (aluminum oxide) and a different phenomenon (optically stimulated luminescence). The results of the theoretical calculations were compared to experimentally determined efficiency data and good agreement (average relative deviation ~ 6%) was found in case of simulations performed using radiation sensitive targets with a diameter of approximately 100 nm. Furthermore, the possibility of determining the optimal target size by using only a subset of the available data was proven successful.