关键词: 镧系硫属化合物, 密度泛函理论, 相对论效应, 键能, 键长

Abstract: The applicability of several density functional formulas to theoretical calculationsof lanthanide chalcogenides has been investigated by per forming calculations on LnL(Ln=La, Gd, Lu 3 L=O, S, Se, Te).The influence of relativistic effects has been considered.The calculated results show that the relativistic effects result in variation of bond lengths from +2 pm to -3 pm, and result in bond energy decrease by 0- 4~O.6 eV, and there is noobvious dependance on the adopted density functional formulas.The difference of densityfunctional formulas does not obviously affect the calculated bond lengths, but signifacantlyinfluence the calculated bond energies.It is found that LDA (VWN) +PW86x scheme givesthe best bond energy.The gradient correction of exchange energy obviously improves thecalculated bond energies, whereas the gradient correction of correlation energy worsen theresults, in consistency with previous conclusions.The simple X_α formula gives pretty goodcalculated bond energies.Taking the relativistic effects and suitable gradient corrections intoaccount,the density functional method gives satisfactory bond lengths, while the calculatedbond energies are still too high, although the relative deviation does not exceed 20%.

Key words: Lanthanide chalcogenides, Density functional theory(DFT), Relativistic effect, Bond length, Bond energy