## 1 Introduction
[PERSON] and co-worker measured the discharge current of polyester film using the isothermal relaxation current method and thermal stimulation current method and found that there was a polarity reversal of the discharge current in the untreated samples. It is believed that the discharge current is a result of the combined action of dipole spin off and space charge dissipation, and the fundamental reason for current polarity reversal is the space charge in the dielectric [12]. [PERSON] and co-worker used a fluid model to simulate the charge transport process in LDPE, which was in good agreement with the electroacoustic method, discharge current and luminous intensity measurement results [13; 14]. [PERSON] and co-worker simulated the existence of a single level trap and exponential level trap in polyethylene and found significant differences in the space charge distribution and discharge current obtained from these two models [15]. [PERSON] and co-worker used fluid simulation to simulate the process of charge trapping and detachment [16]. [PERSON] and co-worker simulated the dynamic change characteristics of the space charge of polyethylene under polarity reversal [17]. The value of electron affinity energy is usually used in theoretical calculations to determine the insulation performance of materials and follows the rule that the greater the electron affinity, the better the insulation performance [18]. However, [PERSON] and co-worker studied the space charge dissipation characteristics of polyethylene using the electroacoustic pulse method [19]. The results show that the space charge transfer rate and crystallinity of silicone oil cooled polyethylene are both large, and the electron affinity is also large. This result means that the electron mobility is a better criterion of the electrical resistance of materials. [PERSON] and co-worker [20] developed a theoretical scheme to predict the carrier mobility of triphenylamine materials, which involves the Marcus electron transfer theory, a direct diabatic dimer model and the Brownian diffusion assumption. The design strategies of circular or linear dimers have been evaluated by the theoretical calculation results of carrier mobility. It was discovered that as for the triphenylamine dimer, because of the difference in the reorganization energy, macrocyclic dimers possess higher mobility than linear chain dimers. We will theoretically analyze polyethylene insulation materials from the perspective of electron mobility. Therefore, in this study, 3-Methylpentane (Pe) was selected as the model molecule for polyethylene. Density functional theory (DFT) was used to analyze the influence of electron-withdrawing and electron-donating groups on electron mobility at the atomic and molecular levels. wB97 XD is an all electron exchange integration recovery (EX-I-R) method used to calculate the interaction energy and other physical quantum chemical quantities of complex molecules, such as the electronic structure, band states, and spectra. The wB97 XD function is based on the wave function method and combines electron exchange and integration operations to achieve more accurate calculation results and can greatly reduce the time and cost of calculations [21]. The electron mobility can provide ideas and directions for the prediction of the electrical resistance of polyethylene insulation materials.