Carreón-Macedo José-Luis, Harvey Jeremy N
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
Phys Chem Chem Phys. 2006 Jan 7;8(1):93-100. doi: 10.1039/b513325d. Epub 2005 Nov 1.
Large basis CCSD(T) calculations are used to calculate the energetics of 3Fe(CO)4, 1Fe(CO)4 and 1Fe(CO)4(L), L = Xe, CH4, H2 and CO. . The relative energy of the excited singlet state of Fe(CO)4 with respect to the ground triplet state is not known experimentally, and various lower levels of theory predict very different results. Upon extrapolating to the infinite basis set limit, and including corrections for core-core and core-valence correlation, scalar relativity, and multi-reference character of the wavefunction, the best CCSD(T) estimate for the spin-state splitting in iron tetracarbonyl is 2 kcal mol(-1). Calculation of the dissociation energy of 1Fe(CO)4(L) into singlet fragments, taken together with known experimental behaviour of triplet Fe(CO)4, provides independent evidence for the fact that the spin-state splitting is smaller than 3 kcal mol(-1). These calculations highlight some of the challenges involved in benchmark calculations on transition metal containing systems.
大基组CCSD(T)计算用于计算3Fe(CO)4、1Fe(CO)4和1Fe(CO)4(L)（L = Xe、CH4、H2和CO）的能量。Fe(CO)4激发单重态相对于基态三重态的相对能量尚无实验测定，不同层次的理论预测结果差异很大。外推至无限基组极限，并包括核对核、核对价相关、标量相对论以及波函数的多参考特征的校正后，四羰基铁自旋态分裂的最佳CCSD(T)估计值为2千卡/摩尔（-1）。将1Fe(CO)4(L)分解为单重态碎片的解离能计算，与三重态Fe(CO)4的已知实验行为相结合，为自旋态分裂小于3千卡/摩尔（-1）这一事实提供了独立证据。这些计算突出了含过渡金属体系基准计算中涉及的一些挑战。
