Study On The Structural Modulation Of Group ?A-?A Compounds And Boron-nitrogen Compound B₉N₉ Structure Modulation By External Electric Field

As an important means of regulating the properties of molecules and materials,germanium sulfide(GeS)can usually change the geometric structure,electronic structure and excitation properties of molecules to change the properties of materials;germanium GeS belongs to group IVA-VIA compounds with narrow band gap characteristics,GeS is widely used in optoelectronics,catalysis and other fields,and has outstanding hot properties,so many scholars have conducted Therefore,many scholars have conducted different degrees of modification studies on GeS.Boron nitride(BN)fullerene materials have excellent electronic and chemical properties and are therefore widely used in electronic devices,hydrogen storage,adsorption,etc.With the development of material synthesis technology,BN nanotubes and BN clusters have been synthesized one after another,and the structure and properties of BN materials have been extensively studied.2019 Science first reported the observation of cyclo[18]carbon in the condensed phase,which presents a very unique geometric and electronic structure,thus attracting widespread attention from the academic community.B in main group III has one less valence electron than C in IV,while N in main group V has one more valence electron than C.Therefore,ring B₉N₉ is isoelectronic with cyclo[18]carbon.Optimization calculations show that the geometry of ring B₉N₉ is similar to the ring structure of cyclo[18]carbon,and the two have many similar physical properties.Therefore,it is of theoretical value to investigate B₉N₉.This thesis uses quantum chemical calculations by applying electric fields of different intensities to GeS and B₉N₉,respectively.1.The external electric field can cause significant structural deformation of GeS.In particular,when the external electric field is large enough(about 0.0395 a.u.),the bond length is significantly elongated in the direction of the external electric field and the bond level is significantly weakened,which is caused by the combined effect of the external electric field and the electric field inside the molecule to move the atoms.In addition,the external electric field makes the charge redistribution inside GeS,causing the molecular polarization,and this effect is more obvious with the strengthening of the electric field intensity,which causes the sharp change of the dipole moment inside the molecule,resulting in a smaller energy of the system.2.The external electric field has a significant modulating effect on the light absorption properties of GeS.When the external electric field is 0.03 a.u.,a new absorption peak appears in the visible region,which is mainly caused by the jump of???*orbitals after orbital analysis,and this modulation has a certain enhancement for the catalytic hydrolysis of GeS in visible light.3.the ring structure of B₉N₉ molecule under the action of external electric field is severely deformed from similar round to elliptical,and the bonding level of Laplace bond is obviously weakened with the increase of external electric field intensity,which is mainly caused by the charge transfer inside the molecule caused by external electric field and the change of force on the atoms.4.the addition of external electric field will cause the electronic structure of B₉N₉ molecule to change thus making the nonlinear optical properties appear,with the increase of the external electric field intensity,the polarization of the molecule becomes more and more intense,showing obvious nonlinear optical effects;at the same time,the change of the electronic structure will also cause the change of the reactive site distribution of B9N9,after the Fukui function based on the double descriptor of the reactive site of the molecule It is predicted that when the external electric field is equal to 0.0365 a.u.,a clear separation between the sites of electrophilic and nucleophilic reactions appears.