| Ionic liquids are compounds composed entirely of cations and anions that exhibit a liquid state at temperatures below 100 degrees Celsius.Ionic liquids,as a new type of soft functional material,have attracted increasing attention in applications such as supercapacitors,new electrolytes,and green chemistry.Furthermore,vibrational spec-troscopy is a powerful tool for detecting liquid structures and characterizing intermolec-ular interactions,with rich information about ionic liquid structure and dynamic pro-cesses contained in the spectral peaks.In addition,ionic liquids exhibit a rich variety of new states under strong magnetic fields.By studying the effects of magnetic fields on the vibrational spectra of ionic liquids,there is important exploratory significance for discovering the regularities of these new states under magnetic fields and their underly-ing mechanisms.In this paper,the effects of magnetic fields of different strengths on the vibra-tional spectra of ionic liquids were studied based on the classical molecular dynam-ics simulation method.The imidazole-type ionic liquid 1-butyl-3-methylimidazolium bis（trifluoromethylsulfonyl）imide（[BMIM][NTf2]）was used as the research object.Firstly,a spatial model of a system with a length,width,and height of 8.0nm containing512 pairs of[BMIM][NTf2]ion pairs was established,with the OPLS-AA and CL&P force field parameters chosen.The equilibrium state resulted in the system’s spatial volume becoming smaller,forming a cube with dimensions of 6.29 nm in length,width,and height.Subsequently,magnetic fields of different intensities were applied,and the above calculation process was repeated to obtain information on the motion trajec-tory of the ionic system under different magnetic field strengths.Multiple core parallel calculations were carried out using the XH321 V5 model of the Lanzhou University high-performance computing platform,which has a specification of 2*Intel Xeon Gold6248 CPUs,to obtain the vibrational spectra of the cations and anions of the ionic liquid[BMIM][NTf2]and the vibrational spectra of the ionic liquid system at the nanoscale under magnetic fields of 0-250MT.The vibrational peaks obtained by the calculations were assigned based on the related research on the vibrational spectra of ionic liquids and the vibrational spectra of individual ionic liquids calculated by density functional theory.The vibrational spectra of the cations and anions under different magnetic field strengths and the vibrational spectra of the ionic liquid were studied segment by seg-ment.The vibrational peaks were divided into five frequency ranges.Subsequently,the changes in the vibrational peaks in each frequency range with increasing magnetic field strength were analyzed.The vibrational spectra exhibit some vibrational peaks that are attributed to the same vibrational mode.In the anion’s vibrational spectrum,the vibrational peaks near the frequencies of 533.41 cm-1and 563.95 cm-1both belong to the bending vibrational mode of the C-F bond in the anion.The intensity of the vibrational peaks decreases monotonically with the increase of the external magnetic field.The intensities of the vibrational peaks at 533.41 cm-1and 563.95 cm-1under a magnetic field of 250MT are 0.142 and 0.098 times that of the vibrational peak intensity without the external magnetic field,respectively.The peak positions of the vibrational peaks show a blue shift with the increase of the magnetic field.A similar paper analyzes the variation of the main vibration peaks in the spectrum.According to the calculated atomic trajectory data,the distribution function of bond Angle and bond length in functional groups in ionic liquid is calculated,and the microscopic mechanism of the change of vibration spectrum is explained by studying the change law of the distribution function.Finally,the vibrational spectra of ionic liquid system in nanometer scale were analyzed by combining the change of vibrational spectra in anion and cation with the enhancement of magnetic field intensity.It is found that anions have a greater influence on the vibration spectrum in the lower frequency band,while cations have a greater influence on the vibration spectrum in the higher frequency band.The amplitude of the vibration mode of the anion usually decreases with the strength of the magnetic field.The amplitude of the vibration mode of the cation is that the influence on the low-frequency vibration spectrum decreases with the enhancement of the magnetic field intensity,and the influence on the high-frequency vibration spectrum increases with the enhancement of the magnetic field intensity. |
