Ab initio studies of the structure and the interaction of cellulose III I crystal
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Ab initio studies of the structure and the interaction of cellulose IIII crystal Kazuyoshi Ueda*, Tetsuya Ishikawa, Hitomi Miyamoto and Daichi Hayakawa Department of Chemistry, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama, Kanagawa 240-8501, JAPAN ABSTRACT Cellulose is one of the most abundant renewable resources and has high potential for the use as a future energy and materials for the chemical industries. We have investigated the crystal structure of cellulose IIII by using first principle density functional theory (DFT) calculation. The geometry optimization was performed with variable-cell relaxation with the Quantum ESPRESSO program package. We used Perdew-Burke-Ernzerhof (PBE) functional and compared the results with long-range van der Waals type correction term approach (PBE-D). The results are in good agreement with the experimentally obtained crystal structure of cellulose IIII when we used the PBE-D. Although the calculated cell parameters were slightly smaller than the experimental one, it can be well explained to include the thermal expansion effect in the experimental condition of ambient temperature. From the optimized crystal structure, the CH/O interactions included in the crystal structure were evaluated using NBO method. In this work, we showed that the density functional calculation is a powerful method to investigate the detail structure and the arrangement in the crystal and the nano-structured materials. INTRODUCTION Cellulose is one of the most abundant renewable resources and has high potential for the use as a future energy and chemical materials. For cellulose crystal, it is known that there are various kind of polymorphs which can be prepared using the different pretreatments. Cellulose I is known as a native cellulose crystal structure, and it can be converted to cellulose IIII by the treatment with liquid ammonia or some amines such as ethylenediamine. Compared to the native cellulose I, cellulose IIII is known to have good accessibility and the reactivity for the cellulose derivatives production and the conversion to the ethanol or to the chemical resources. For a further application for these field, it is important to know the accurate knowledge of the basic information of the crystal structure and the phase transition mechanism of the polymorphs of the cellulose. In this study, we try to apply the density functional calculation method to investigate the crystal structure of cellulose IIII in more detail. The crystal structure of cellulose IIII has been investigated by X- ray diffraction, NMR,IR and computational theoretical calculation methods for many years.1-3 Recently, Wada et al. 4 proposed a new crystal structure of cellulose IIII, which has monoclinic P21 space group with a cell dimension of a = 0.445 nm, b = 0.785 nm, c(chain axis) = 1.031 nm and γ = 105.1 by their X-ray and neutron diffraction experiments using highly oriented fiber sample of cellulose IIII. This model shows in a good accordance with the CP/MAS 13C NMR spect
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