团簇Fe_3Cr_3的结构稳定性与成键

Analysis on structural stability and bonding of cluster Fe_3Cr_3

依据密度泛函理论(DFT)中的B3LYP/Lan12dz方法对团簇Fe_3Cr_3的初始构型进行优化计算,最终得到15种稳定构型,分别为单帽三角双锥型、五棱锥型和四角双锥型。对单、三重态下每个优化构型的校正能(E_(ZPE))、吉布斯自由能(G)、结合能(EBE)和吉布斯自由能变(△G)4个能量参数进行比较分析,并分别研究不同成键类型的平均键长、平均键级和键级贡献比例。结果表明:团簇Fe_3Cr_3三重态下的构型普遍比单重态稳定。其中,构型1(3)稳定性最好;构型7(1)稳定性最差。Fe-Fe成键键级是单、三重态构型稳定性的主要贡献者,但多重度影响其成键强度,且其在三重态构型中的贡献比例高于单重态构型。三重态构型中Cr-Cr成键贡献最少,而单重态构型中Fe-Cr成键贡献最少,同时其键级占比小于两个重态下其它的成键类型。

By using B3LYP/Lan12 dz method of density functional theory（DFT）,optimization calculations on initial configurations of cluster Fe3Cr3 were performed. Fifteen stable configurations were obtained in forms of single-cap triangular bipyramid,pentagonal pyramid and quadrangular bipyramid. The correction energy（EZPE）,Gibbs free energy（G）,binding energy（EBE）and Gibbs free energy change（△G）of each optimized configuration in singlet and triplet states were compared and analyzed,and the average bond length,average bond order and contribution ratio of bond order for different bonding types were studied. The results show that the cluster Fe3Cr3 is generally more stable in singlet state than in triplet state,in which the configuration 1（3）has the best stability whereas the configuration 7（1）has the worst. Fe-Fe bonding order is the main contributor to the stability of the singlet and triplet configurations but its bonding strength is affected by multiplicity,and its contribution is higher to the triplet configurations than o the singlet configurations. In the triplet configuration Cr-Cr bonding contribution is the least,while in the singlet configuration,Fe-Cr bonding contribution is the least and,at the same time,its bond order contribution proportion is less than two other bonding types.