Study On External Electric Field Characteristics Of SF₆ Alternative Gas C₄F₇N

SF₆ is widely used as a high quality insulation gas in the field of high voltage and insulation.However,SF₆ is one kind of greenhouse gas.In response to international environmental protection requirements and national sustainable development strategies,it is an important part of the current development of high-voltage insulation field to find a new environmentally friendly alternative to SF₆ to realize reliable insulation.C₄F₇N stands out from a large number of research objects for its good insulation performance,arc extinguishing performance and environmental protection characteristics,and has become a research hotspot for many scholars.The structure of C₄F₇N molecule is clear and stable,but it is unknown whether and how the structure,chemical stability and electrical properties of C₄F₇N molecule change under the influence of external electric fields.Molecular simulation technology reflects the macroscopic characteristics of molecules by calculating the relevant parameters of atoms and electrons.Its application in the field of high-voltage insulation has just begun.In this project,the electron density,atomic charge,and system energy of C₄F₇N molecule under different electric fields are calculated and analyzed by applying electric field inside the molecule based on the quantum chemistry theory and the density functional theory,so that the molecular structures,Fukui functions,ionization energies and electronegativities can be calculated to reflect variations of molecular structure,reactivity,insulation performance and arc-extinguishing performance under external electric fields.In order to investigate the influence of external electric field on the structural parameters and characteristics of C₄F₇N molecules,a C₄F₇N molecular model is constructed.The bond length,Mulliken charge population and molecular energy are calculated using Minnesota density functional method M06-2X at the 6-311g（d,p）level,the influence of external electric fields is analyzed.The results show that with the increase of electric field,the charge distribution of each atom changes,resulting in the changes of bond length and total energy,and the molecular structure tends to be unstable.Then the ADCH atomic charges,dipole moments and polarizabilities of C₄F₇N molecule are calculated by using Minnesota density functional method M06-2X and aug-cc-p VTZ basis set.The results show that all three are significantly dependent on the external electric fields.As the external electric field increases,the molecular polarity increases,the volume increases,and the stability decreases.Compared with SF₆,the dipole moment and polarizability of C₄F₇N molecules are higher on the whole,and C₄F₇N is more affected by external electric fields,and its stability is weaker.At the same time,in order to investigate the effect of external electric fields on the chemical stability and electrical properties of C₄F₇N molecules,the B3LYP functional method and 6-311G*basis set are used to calculate the Fukui functions,condensed Fukui functions,ionization energies and electronegativities of C₄F₇N.The results show that the reactive sites of C₄F₇N molecule are 4C,5N and 12F,5N is the most active,and the CFF of each atom changes regularly under the action of external electric field.Affected by the electric fields,the dielectric strength and arc extinguishing performance of C₄F₇N are enhanced,and it can reach a good level close to SF₆.If no electric field,its electronegativity is 0.77 times that of pure SF₆ and 1.15 times that of c-C₄F₈,and ionization energy is 0.85 times of pure SF₆ and 1.11 times of c-C₄F₈.To some extent,the c-n triple bond is more capable of promoting the electrical properties than the C-ring in a4-C structure.The above work fully demonstrates that the external electric field has significant effects on the structure,chemical stability,insulation performance and arc extinguishing performance of C₄F₇N molecules.It provides a quantitative basis for the realization of replacing SF₆ with C₄F₇N as an environmentally friendly insulating gas,and also verifies the feasibility of molecular simulation technology for the research of insulating gases,shows the unique charm of quantum chemical computational analysis in the field of high voltage insulation,and paves a promising avenue for the research of new insulating gases.