Réal Florent, Vallet Valérie, Flament Jean-Pierre, Schamps Joël
Laboratoire PhLAM, Université des Sciences et Technologies de Lille 1, CNRS UMR 8523, F-59655 Villeneuve d'Ascq Cedex, France.
J Chem Phys. 2006 Nov 7;125(17):174709. doi: 10.1063/1.2361293.
Ab initio study of excitation energies and oscillator strengths for absorption towards the (3)P(1) and (1)P(1) states of the Bi(3+) ion has been performed for the Bi(3+) ion in gas phase and as a dopant of the cubic elpasolite Cs(2)NaYCl(6) and the yttria Y(2)O(3) crystal using the ab initio embedded-cluster method. The ground and excited states were computed with a relativistic spin-orbit configuration interaction approach suited for heavy elements. Electron correlation was treated in the scalar relativistic scheme with perturbative, variational, and coupled-cluster methods. Intermediate coupling is included via an effective-Hamiltonian based spin-orbit configuration interaction approach. Small-core (60 electrons) and large-core (78 electrons) relativistic effective core potentials (ECPs) have been used to describe the bismuth ion. The best match with experiment was obtained with the small-core ECP. The accuracy of excitation energies strongly depends on the electron correlation method used. The agreement between experimental data and the results obtained using second-order multiconfigurational perturbation theory is greatly improved with the shifted zeroth-order Hamiltonian proposed by Ghido et al. [Chem. Phys. Lett. 396, 142 (2004)]. Although quite time consuming, coupled-cluster and variational methods yield good agreement with experimental data. The first absorption band recorded for the doped elpasolite crystal is positioned with an excellent accuracy while the computed energy of the second absorbing manifold is in poorer agreement with experimental data. This suggests that interactions with neglected close-lying excited states with a ligand-to-metal charge transfer character may be significant. Calculations of the spectrum of Bi(3+) doping yttria in both the S(6) and C(2) site symmetries indicate that the absorbing manifold arises from electronic excitations localized on the Bi(3+) doping ion with main triplet 6s6p character. Our results predict the first absorbing peak to lie about 0.5 eV lower for the S(6) sites than for the C(2) site, thus attributing the violet and the green emission wavelengths to the S(6) and C(2) sites, respectively. A subsequent study of Stokes shift and emission wavelength should hopefully lead to a final assignment of the measured excitation spectra.
采用从头算嵌入簇方法，对气相中的Bi(3+)离子以及作为立方铯榴石Cs(2)NaYCl(6)和氧化钇Y(2)O(3)晶体掺杂剂的Bi(3+)离子，针对向Bi(3+)离子的(3)P(1)和(1)P(1)态吸收的激发能和振子强度进行了从头算研究。基态和激发态采用适合重元素的相对论自旋轨道组态相互作用方法进行计算。电子相关在标量相对论方案中采用微扰、变分和耦合簇方法处理。通过基于有效哈密顿量的自旋轨道组态相互作用方法纳入中间耦合。小核（60个电子）和大核（78个电子）相对论有效核势（ECP）已用于描述铋离子。使用小核ECP获得了与实验的最佳匹配。激发能的精度强烈依赖于所使用的电子相关方法。Ghido等人[《化学物理快报》396, 142 (2004)]提出的移位零阶哈密顿量极大地改善了实验数据与使用二阶多组态微扰理论获得的结果之间的一致性。尽管相当耗时，但耦合簇和变分方法与实验数据取得了良好的一致性。对于掺杂的铯榴石晶体记录的第一个吸收带定位精度极高，而计算得到的第二个吸收多重态的能量与实验数据的一致性较差。这表明与具有配体到金属电荷转移特征的被忽略的近邻激发态的相互作用可能很显著。对Bi(3+)掺杂氧化钇在S(6)和C(2)位对称下的光谱计算表明，吸收多重态源于Bi(3+)掺杂离子上局域化的电子激发，主要具有三重态6s6p特征。我们的结果预测，S(6)位的第一个吸收峰比C(2)位低约0.5 eV，因此分别将紫色和绿色发射波长归因于S(6)和C(2)位。随后对斯托克斯位移和发射波长的研究有望最终确定测量的激发光谱。
