Density functional study of Fe2 N2

✍ Scribed by Angelica Zacarias; Miguel Castro

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 724 KB
• Volume: 60
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1996)60:7<1419::aid-qua24>3.0.co;2-y

✦ Synopsis

The interaction of two iron atoms with molecular nitrogen was studied by means of density functional techniques. Calculations were of the all-electron type, and both conventional local and gradient-dependent approximate (GDA) models were used. A ground state (GS) of linear structure was found for Fez-N, with 2s + 1 = 7; whereas a distorted tetrahedral structure, being also a septuplet, was located at 4.0 and 14.3 kcal/mol above the GS, at the local and GDA levels of theory, respectively. The N-N bond is moderately perturbed in the GS, but it is strongly activated in the tetrahedral mode: It has bond orders of 2.6 and 1.5, vibrational frequencies of 2148 and 1496 cm-', and equilibrium bond lengths of 1.14 and 1.24 A, for the @ear and tetrahedral geometries, respectively. These values are 3.0,2359 cm-', and 1.095 A, for free N,. At GDA level of theory, the Fez-N, binding energy is 15 kcal/mol, which is bigger than that of Fe-N, (9 kcal/mol). The 7r-back donation, in the linear GS, is of 0.31 electrons, but the total charge transfer, from Fez to N,, is only 0.05 units. This is relevant in comparison with the tetrahedral mode, where the Fez to N, total charge transfer is of 0.45 electrons, yielding a stronger activated N, moiety.