Cernusák Ivan, Dallos Michal, Lischka Hans, Müller Thomas, Uhlár Milan
Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, SK-84215 Bratislava, Slovakia.
J Chem Phys. 2007 Jun 7;126(21):214311. doi: 10.1063/1.2741522.
The electronic structure of a series of low-lying excited triplet and quintet states of scandium boride (ScB) was examined using multireference configuration interaction (including Davidson's correction for quadruple excitations) and single-reference coupled cluster (CC) methods with averaged natural orbital (ANO) basis sets. The CC approach was used only for the lowest quintet state. The authors have analyzed eight low-lying triplets 3Sigma-(2), 3Sigma+, 3Pi(3), and 3Delta(2) dissociating to Sc(2D)/B(2P) atoms and eight low-lying quintet states 5Sigma-, 5Sigma+, 5Pi(2), 5Phi, and 5Delta(3) dissociating to Sc(4F)/B(2P) atoms. They report the potential energy curves and spectroscopic parameters of ScB obtained with the multireference configuration interaction (MRCI) technique including all singly and doubly excited configurations obtained with the ANO-S basis set. For the two lowest states they obtained also improved ANO-L spectroscopic constants, dipole and quadrupole moments as well as scalar relativistic effects based on the Douglas-Kroll-Hess Hamiltonian. They provide the analysis of the bonding based on Mulliken populations and occupation numbers. Since the two lowest states, 3Sigma- and 5Sigma-, lie energetically very close, their principal goal was to resolve the nature of the ground state of ScB. Their nonrelativistic MRCI(Q) (including Davidson correction) results indicate that the quintet is more stable than the triplet by about 800 cm(-1). Inclusion of scalar relativistic effects reduces this difference to about 240 cm(-1). The dissociation energies for 5Sigma- ScB range from 3.20 to 3.30 eV while those for the 3Sigma- range from 1.70 to 1.80 eV.
使用多参考组态相互作用（包括对四重激发的戴维森校正）和单参考耦合簇（CC）方法以及平均自然轨道（ANO）基组，研究了一系列硼化钪（ScB）的低激发三重态和五重态的电子结构。CC方法仅用于最低的五重态。作者分析了八个解离为Sc(2D)/B(2P)原子的低激发三重态3Σ-(2)、3Σ+、3Π(3)和3Δ(2)，以及八个解离为Sc(4F)/B(2P)原子的低激发五重态5Σ-、5Σ+、5Π(2)、5Φ和5Δ(3)。他们报告了使用多参考组态相互作用（MRCI）技术获得的ScB的势能曲线和光谱参数，该技术包括使用ANO-S基组获得的所有单重和双重激发组态。对于两个最低态，他们还基于道格拉斯-克罗尔-赫斯哈密顿量获得了改进的ANO-L光谱常数、偶极矩和四极矩以及标量相对论效应。他们基于穆利肯布居数和占据数对键合进行了分析。由于两个最低态3Σ-和5Σ-在能量上非常接近，他们的主要目标是确定ScB基态的性质。他们的非相对论MRCI(Q)（包括戴维森校正）结果表明，五重态比三重态稳定约800 cm(-1)。包含标量相对论效应将这种差异减小到约240 cm(-1)。5Σ- ScB的解离能范围为3.20至3.30 eV，而3Σ-的解离能范围为1.70至1.80 eV。
