Tzeli Demeter, Miranda Ulises, Kaplan Ilya G, Mavridis Aristides
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Ave., Athens 116 35, Greece.
J Chem Phys. 2008 Oct 21;129(15):154310. doi: 10.1063/1.2993750.
We have examined the electronic structure and bonding of the Mn(2) molecule through multireference variational calculations coupled with augmented quadruple correlation consistent basis sets. The Mn atom has a (6)S(4s(2)3d(5)) ground state with its first excited state, (6)D(4s(1)3d(6)), located 2.145 eV higher. For all six molecular states (1)Sigma(g)(+), (3)Sigma(u)(+), (5)Sigma(g)(+), (7)Sigma(u)(+), (9)Sigma(g)(+), and (11)Sigma(u)(+)(1) correlating to Mn((6)S)+Mn((6)S), and for six undecets, i.e., (11)Pi(u), (11)Sigma(g)(+), (11)Delta(g), (11)Delta(u), (11)Sigma(u)(+)(2), and (11)Pi(g) with end fragments Mn((6)S)+Mn((6)D), complete potential energy curves have been constructed for the first time. We prove that the bonding in Mn(2) dimer is of van der Waals type. The interaction of two Mn (6)S atoms is hardly influenced by the total spin, as a result the six Sigma states, singlet ((1)Sigma(g)(+)) to undecet ((11)Sigma(u)(+)(1)), are in essence degenerate packed within an energy interval of about 70 cm(-1). Their ordering follows the spin multiplicity, the ground state being a singlet, X (1)Sigma(g)(+), with binding energy D(e) (D(0)) approximately 600 (550)cm(-1) at r(e) approximately 3.60 A. The six undecet states related to the Mn((6)S)+Mn((6)D) manifold, are chemically bound with binding energies ranging from 3 ((11)Pi(g)) to 25 ((11)Pi(u))kcal/mol and bond distances about 1 A shorter than the states of the lower manifold, Mn((6)S)+Mn((6)S). The lowest of the undecets is of Pi(u) symmetry located 30 kcal/mol above the X (1)Sigma(g)(+) state.
我们通过多参考变分计算结合增强四重相关一致基组，研究了Mn₂分子的电子结构和键合。锰原子基态为(⁶S)(4s²3d⁵)，其第一激发态(⁶D)(4s¹3d⁶)比基态高2.145 eV。对于所有六个与Mn((⁶S))+Mn((⁶S))相关的分子态(¹Σg⁺)、(³Σu⁺)、(⁵Σg⁺)、(⁷Σu⁺)、(⁹Σg⁺)和(¹¹Σu⁺)(¹)，以及六个十一重态，即(¹¹Πu)、(¹¹Σg⁺)、(¹¹Δg)、(¹¹Δu)、(¹¹Σu⁺)(²)和(¹¹Πg)，其末端片段为Mn((⁶S))+Mn((⁶D))，首次构建了完整的势能曲线。我们证明Mn₂二聚体中的键合属于范德华类型。两个Mn(⁶S)原子的相互作用几乎不受总自旋的影响，因此六个Σ态，从单重态(¹Σg⁺)到十一重态(¹¹Σu⁺)(¹)，本质上在约70 cm⁻¹的能量区间内简并堆积。它们的排序遵循自旋多重性，基态是单重态，X¹Σg⁺，在r(e)约为3.60 Å时，结合能D(e)(D(0))约为600(550)cm⁻¹。与Mn((⁶S))+Mn((⁶D))多重态相关的六个十一重态是化学键合的，结合能范围从3((¹¹Πg))到25((¹¹Πu))kcal/mol，键长比低多重态Mn((⁶S))+Mn((⁶S))的态短约1 Å。最低的十一重态具有Πu对称性，比X¹Σg⁺态高30 kcal/mol。
