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- Title
Molecular Modeling of Organic Corrosion Inhibitors: Why Bare Metal Cations are Not Appropriate Models of Oxidized Metal Surfaces and Solvated Metal Cations.
- Authors
Kokalj, Anton
- Abstract
The applicability of various models of oxidized metal surfaces -- bare metal cations, clusters of various size, and extended (periodic) slabs -- that are used in the field of quantum-chemical modeling of corrosion inhibitors is examined and discussed. As representative model systems imidazole inhibitor, MgO surface, and solvated Mg2+ ion are considered by means of density-functional-theory calculations. Although the results of cluster models are prone to cluster size and shape effects, the clusters of moderate size seem useful at least for qualitative purposes. In contrast, the bare metal cations are useless not only as models of oxidized surfaces but also as models of solvated cations, because they bind molecules several times stronger than the more appropriate models. In particular, bare Mg2+ binds imidazole by 5.9 eV, while the slab model of MgO(001) by only 0.35 eV. Such binding is even stronger for 3+ cations, e.g., bare Al3+ binds imidazole by 17.9 eV. The reasons for these fantastically strong binding energies are discussed and it is shown that the strong bonding is predominantly due to electron charge transfer from molecule to metal cation, which stems from differences between molecular and metal ionization potentials.
- Subjects
CORROSION &; anti-corrosives; MOLECULAR models; METAL ions; METALLIC surfaces; OXIDATION; SOLVATION; QUANTUM chemistry
- Publication
Acta Chimica Slovenica, 2014, Vol 61, Issue 2, p340
- ISSN
1318-0207
- Publication type
Article