Atomic and Electronic Structures of Molecular Crystalline Cellulose I..beta..: A First-Principles Investigation

A theoretical model based on the competition between hydrogen-bonding energy and strain energy was constructed to explain the size of native cellulose Iβ. The cellodextrins in native crystalline cellulose Iα and Iβ are unusually stable compared to other polysaccharides, not easily prone to hydrolysis even though they are only nanometers in diameter. The stability of crystalline cellulose Iβ is most likely due to its greatly enhanced hydrogen-bonding (HB) network. We carried out ab initio calculations to determine the native crystalline cellulose Iβ atomic and conformational structures. For crystalline cellulose, we found that every hydroxyl group in the cellulose structure is hydrogen bonded as both a donor and an acceptor. This agrees well with published X-ray and neutron diffraction data. We also determined the electronic structures and the energetics for one cellodextrin chain, one to four sheets of cellodextrins in cellulose, and the bulk cellulose Iβ.