Analyzing ab initio infrared spectra and electronic properties of polyethylenimine water complexes in the solid state
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- 作者：Guillaume Herlem ; Tijani Gharbi ; Nebiha Ben Sedrine
- 关键词：Polyethylenimine ; Periodic ab initio calculations ; Electron density of states ; Band structure ; IR spectra
- 刊名：Journal of Molecular Structure: THEOCHEM
- 出版年：2010
- 出版时间：15 April 2010
- 年：2010
- 卷：945
- 期：1-3
- 页码：27-32
- 全文大小：363 K
文摘
We focused our study on the hydrated polyethylenimine (PEI) crystals which are characterized by the presence of 0.5, 1.5 or 2 water molecules per ethylenimine monomer unit. We propose a theoretical study in the framework of periodic linear combination of atomic orbitals (LCAO) using different Hamiltonians based on density functional theory (DFT) and hybrid Hartree–Fock (HF) – DFT level of theory. Once hydrogen atoms added when missing and redundant atoms withdrawn in the PEI structures, ab initio calculations yielded relaxed geometries at the ground state. The closest structural parameters to the experimental values are observed for hybrid Hamiltonians and the use of the 6-31++G* basis set reduces this difference. We provide the IR vibration modes at the Γ point, with assignments of the bands. The electronic study reveals that these PEI hydrates have an insulating character with a quasi constant band gap whatever the number of water molecules. From the projected density of states (PDOS), we have found that the nitrogen orbital has the major contribution to the valence band, while the conduction band is mainly constructed from hydrogen bondings.