Electronic Properties of Bio-based Hydrocarbon Liquids Under Extreme Electric Fields: Molecular Insights Into Its Excellent Impulse Insulation Properties Based on DFT and First Principles

Bio-based hydrocarbon liquids have excellent biodegradability, physicochemical properties and impulse insulating properties, and have become the focus of research in recent years. In this paper, using density functional theory (DFT) and first-principles calculations, the variations and differences in ionization energy, electron affinity, excitation processes, and molecular orbital characteristics of isoalkanes (the main component of bio-based insulating oil) and mineral oil molecules under varying electric field intensities were simulated and analyzed. Based on the key microscopic parameters of isoalkanes and mineral oil systems, their impulse insulation properties were comprehensively evaluated. The test results reveal that the ionization potential (IP), excitation energy, and band gap of C22-isoalkanes are the largest, followed by C18-isoalkanes, while those of mineral oil are the smallest. Hydrocarbon insulating liquids exhibit a clear “short board” effect in their ionization energy and excitation energy. Aromatic hydrocarbons with lower ionization energy, excitation energy, and energy gaps in mineral oil significantly influence its overall performance. Consequently, the pulse insulation performance of isoalkanes is similar to or even better than that of mineral oil in theory, which is basically consistent with the experimental results. The isoalkanes with shorter molecular chains are expected to have better pulse insulation performance. This work provides theoretical guidance for understanding the microscopic mechanism of the difference in impulse insulation properties between bio-based hydrocarbon liquids and mineral oils.