LOCAL SPIN-DENSITY INVESTIGATION OF THE CHROMIUM POLYIMIDE INTERFACE

Bonding of chromium to the polyimide, PMDA-ODA, surface is still the s ubject of debate. In an attempt to clarify this problem, we have perfo rmed density functional theory calculations on different model molecul es, phthalimide, PMDA, and PAP (p-amino phenol), which represent the m ost functionalities of the polyimide (PMDA-ODA). If we consider only t he low spin case, we find that chromium bonds preferentially to the ph enyl ring. However, when we release the spin constraint and optimize t he structure, we find that the absolute stable configuration is that o f chromium in a quintet state, at a carbonyl group. The energy differe nce is 0.30 eV. The complete infrared spectrum has been calculated for phthalimide and compared with experimental spectra. The agreement is excellent. A vibrational analysis for the Cr/phthalimide system, in bo th configurations (Cr on C=O and Cr on phenyl), in their stable spin s tates, is presented. We find that the former yields better agreement w ith experiment than the latter.