Calculation of the Ground and Excited States of a Mixed Valence Compound [Fe2(OH)3(NH3)6]2+: A Class II or Class III Compound?

The effective group potentials (EGP) approach has been successfully used for the computation of the ground and
excited states energies of the mixed valence compound [Fe2(OH)3(NH3)6]2+. It is the first time that for a system as
big as the complex presented above the ground and excited states are computed with their own orbitals and
studied in such a detailed way. First of all, the NH3 EGP was validated by comparing calculations where NH3 was
treated explicitly at different levels of calculations. Once the validation was obtained, the complete spectrum of the
compound under interest was calculated and compared with results obtained in a previous work by Barone et al.
and the spin Hamiltonian of widespread use. Some deviations from these predictive approaches were observed.
This allowed us to emphasize the importance of the dynamic correlation which is not included explicitly in the spin
Hamiltonian. Then, the influence of vibration has been studied by computing the potential energy curves obtained
when moving the (OH)3 plane. This study shows that our calculations lead to a delocalized compound (class III)
as expected according to former experimental data.

有效集团势能（EGP）方法已被成功应用于混合价态化合物[Fe2(OH)3(NH3)6]2+的基态和激发态能量的计算。这尚属首次，对于一个如上所述之庞大的系统，其基态和激发态的能量计算采用自身轨道进行，并进行了如此细致的研究。首先，通过将NH3在不同计算水平上显式处理，验证了NH3的EGP。一旦验证成功，便计算了所关注化合物的完整谱系，并将其与Barone等人先前工作的结果以及广泛应用的自旋哈密顿量进行比较。观察到某些预测方法的偏差，这使我们能够强调动态相关性（该相关性在自旋哈密顿量中并未显式包含）的重要性。随后，通过移动(OH)3平面计算了势能曲线，以研究振动的影响。此项研究表明，我们的计算结果与前期实验数据一致，预示着得到了一个离域化合物（III类）。