This paper models the uniaxial compression of a single crystal of commercial purity aluminum, and compares the modeling results with experimental data. The problem is solved using a first-type direct model based on the finite element method. The material behavior is described by a crystal elastoviscoplasticity model that explicitly accounts for shearing on crystallographic planes. The main feature of this study is a physically sound description of the geometric nonlinearity associated with crystal lattice rotation. The modeling results show that the original homogeneous single crystal is divided into volumes with different plastic shear rate intensity and lattice orientation, which is in satisfactory agreement with experimental data.