Design Of Si-doped Fullerenes And Their Nonlinear Optical Propeties

Since the advent of laser,nonlinear optical research has attracted people's attention,and looking for high-performance nonlinear optical materials quickly become a hot research.Fullerenes have a good ?-electron delocalization,and the theory and experiments show a certain degree of nonlinear optical properties.We hope to improve the nonlinear optical properties of fullerenes by introducing heteroatom-modified fullerenes.Silicon and carbon are the same main group,and silicon atoms are easier to polarize than carbon atoms.Because of showing a greater degree of polarization,so silicon as a heteroatom is a good choice.In this paper,the possible role of silicon atoms in enhancing the nonlinear optical properties of fullerenes is studied by theoretical simulation.The main contents include the following three parts:1.Enhanced optical nonlinearity based on silicon ring.We constructed six silicon-like compounds of benzene and polycyclic aromatic hydrocarbons,Si6H6,Si10H8,Si14H10,Si16H10 and Si24H12.The nonlinear optical polarization of these polycyclic silicon hydrogens is significantly enhanced compared to the corresponding polycyclic aromatic hydrocarbons.For example,the third order polarizability of Si10H8 is equivalent to C60 and Si24H12 is 10 times that of C12H12 and C60.The main reason for the enhancement is that the linear absorption spectra of polycyclic silicon hydrogens have a significant red shift relative to the corresponding polycyclic hydrocarbons,and that the two compounds are very similar in electron delocalization.The results show that it is feasible to enhance the nonlinear properties of fullerenes with Si atoms.2.Enhancement of nonlinear optical properties of single Si modified fullerenes.We built the C60C and C60Si configurations.The nonlinear polarizability of these two configurations is much stronger than that of fullerenes.For example,the second order nonlinearity,C60 itself has a high degree of Ih symmetry,the second order nonlinearity is zero.As a result,C60 introduces the heteroatoms,C60C and C60Si have second order nonlinearity,in which the second order nonlinearity of C60Si is larger.For the third-order nonlinearity,? value of C60C static theory calculated value(280.40× 10-36esu)is C60 7 times as much,and ? value of C60Si static theory calculated value(423.13 × 10'36esu)is C60 11 times.It is clear that the Si-modified fullerene is more nonlinear.Therefore,it can be concluded that both the second-order polarizability and the third-order polarizability,the silicon atom modification is better than the carbon atom modification to enhance the nonlinear optical properties of fullerenes.3.Enhancement of nonlinear optical properties of C60C2 and C60CSi.The way of theoretical calculation study the two carbons and two silicon-linked fullerenes and their corresponding nonlinear structure.We have theoretically designed two series of molecules,namely C60C2 and C60CSi.The results show that the second order nonlinearity,only the carbon series of C60C2-trans1 is no second-order nonlinearity,because the structure is too high symmetry and the dipole moment is zero.The other two series of molecules are enhanced relative to the fullerene nonlinearity.In addition,C60C2-cis3 and C60CSi-cis3 corresponded to the ?tot calculated from 0.0 to 2.0 ev,and C60CSi-cis3 was significantly larger than C60C2-cis3.The main reason for the enhancement is that the transition energy of C60CSi-cis3(0.4362eV)is smaller than that of C60C2-cis3(0.5180 eV).In the third-order nonlinearity,the third-order static polarization(408.46 × 10-36esu)of C60CSi-transl is larger than that of C60C2-transl(595.28 × 10-36esu),and the third-order static polarization of C60CSi-cis3(14510.53 × 10-36esu)is nine times larger than C60C2-trans1(1503.53 × 10-36esu),and the results can show that silicon atoms can better enhance the nonlinearity of fullerenes.