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Density functional study of Fe 2 N 2
Author(s) -
Zacarias Angelica,
Castro Miguel
Publication year - 1996
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1996)60:7<1419::aid-qua24>3.0.co;2-y
Subject(s) - bond length , chemistry , density functional theory , tetrahedron , atomic physics , electron , crystallography , charge (physics) , ground state , molecular geometry , electron affinity (data page) , electron transfer , moiety , computational chemistry , physics , molecule , stereochemistry , crystal structure , organic chemistry , quantum mechanics
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 Fe 2 ‐N 2 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 ‐1 , and equilibrium bond lengths of 1.14 and 1.24 Å, for the linear and tetrahedral geometries, respectively. These values are 3.0, 2359 cm ‐1 , and 1.095 Å, for free N 2 . At GDA level of theory, the Fe 2 ‐N 2 binding energy is 15 kcal/mol, which is bigger than that of Fe‐N 2 (9 kcal/mol). The π‐back donation, in the linear GS, is of 0.31 electrons, but the total charge transfer, from Fe 2 to N 2 , is only 0.05 units. This is relevant in comparison with the tetrahedral mode, where the Fe 2 to N 2 total charge transfer is of 0.45 electrons, yielding a stronger activated N 2 moiety. © 1996 John Wiley & Sons, Inc.