Internal partial discharges and treeing are among the main mechanisms of aging in polymeric materials used in electrical networks. A better understanding of these processes requires the creation of well-developed simulation systems based on the numerical solution of first principles expressed through sets of differential equations. The accuracy of predictions from these models critically depends on the quality of the physical parameters used. In particular, the correct representation of the discharge inception through the formation of a primary free electron plays a key role. Inception electrons are mainly injected from the gas-solid interface through the Schottky effect. The work function is the main parameter that characterizes this effect, and thus the quality of the entire simulation depends on it. In this work, this parameter will be estimated from electronic structure simulations of polyethylene, and sensitivity studies will be conducted to assess how variations in this parameter affect the simulations. Specifically, we will assume the polymeric material is polyethylene, as it is extensively used in the electrical industry. The simulations produce data that can be directly compared with experimental measurements to validate the process.