Theoretical Study Of Electronic Structure And Spectroscopic Constants Of The Osmium Silicide

Transition metal complexes have many excellent properties.They are widely used in catalytic chemistry,thermoelectric materials,electronic components and so on.Theoretical studies of diatomic transition metal complexes have important theoretical significance for understanding the nature of the chemical bond formed,electronic structure and spectrum of the complexes,and the like.This article will conduct a detailed study for the OsSi molecular spectrum from theoretical calculations.Resonant two-photon ionization spectroscopy of jet-cooled OsSi has been obtained in the experiment.There have been theoretical studies that only considered the scalar relativistic effect,although ignored spin-orbit couplings.Since relativistic effect of Os is very strong,so the results obtained show that there is insufficient to resolve the molecular spectrum of OsSi.In order to consider the zero field splitting effect,spin orbit coupling must be included in the calculation.In this paper,a high-precision multi-reference electron correlation calculation method is used,namely the multi-state N-electron valence state second-order perturbation theory?MS-NEVPT2?,combined with the ANO-RCC relativistic basis set,the DKH2 Hamiltonian,and the use of state interactions to consider the spin-orbit coupling.Therefore,the electronic states of OsSi are carefully calculated.The ground state of our result is X ³?₀₊^-,which is consistent with the experimental result.The theoretical equilibrium bond length 2.103?is close to the experimental measurement of 2.1207?while the vibrational frequency 466 cm^-1is smaller than the experimental value of 516 cm^-1.Theoretical calculations show that the A-X system is equivalent to the excitation of ³???₁????X ³?₀₊^-in the experiment,and the theoretical adiabatic excitation energy 15568cm^-1 is very close to the experimental value of 15728 cm^-1.In addition,the B-X system in the experiment should be referred to as the excitation of ³???₁????X ³?₀₊^-,and the theoretical adiabatic excitation energy 18316 cm^-1is very close to the experimental value of 18469 cm^-1.In particular,the oscillator strength of ³???₁????X ³?₀₊^-in the theoretical calculations is larger than the oscillator strength of ³???₁????X ³?₀₊^-,which is inconsistent with the experimental result,suggesting that there may be an intermediate state,with ³???₁???coupling weakens the intensity of the ³???₁????X ³?₀₊^-,and we think that this intermediate state is ³???₀₊???.Moreover,because there is no theoretical support,previous experiments have indicated that the leading configuration of ³???₁???and ¹???₁???of OsSi is obtained by comparing the theoretical calculation results with the equivalent electronic WO,so it is not reliable.We calculate that the leading configuration of the upper states of the experimental recorded spectrum should be 17?²18?²9?³4?³,which is formed by the excitation of electron from 9? to 4?.With OsSi isovalent molecule OsC,its the ground state has a big controversial between the experimental result and theoretical calculation.We adopt the same methods as OsSi and consider spin-orbit coupling effect to calculate the spectral constants of the low-lying of OsC.Analyze the data and finally determine its ground state.