Anisotropy and temperature dependence of structural, thermodynamic, and elastic properties of crystalline cellulose I_β: a first-principles investigation

Abstract

Anisotropy and temperature dependence of structural, thermodynamic and elastic properties of crystalline cellulose I β were computed with first-principles density functional theory (DFT) and a semi-empirical correction for van der Waals interactions. Specifically, we report the computed temperature variation (up to 500 K) of the monoclinic cellulose I β lattice parameters, constant pressure heat capacity, C p , entropy, S, enthalpy, H , the linear thermal expansion components, ξ i , and components of the isentropic and isothermal (single crystal) elastic stiffness matrices, C S ij (T ) and C T ij (T ), respectively. Thermodynamic quantities from phonon calculations computed with DFT and the supercell method provided necessary inputs to compute the temperature dependence of cellulose I β properties via the quasi-harmonic approach. The notable exceptions were the thermal conductivity components, λ i (the prediction of which has proven to be problematic for insulators using DFT) for which the reverse, non-equilibrium molecular dynamics approach with a force field was applied. The extent to which anisotropy of Young's modulus and Poisson's ratio is temperature-dependent was explored in terms of the variations of each

Evaluation of reactive force fields for prediction of the thermo-mechanical properties of cellulose Iβ

“…However, the specific crystallographic orientation with respect to the loading direction was unknown during the tests due to the variability in particle shape and lack of control of how they lie on the substrate, leading to large variability in the Young's modulus data. For a more comprehensive discussion see Dri et al [8] and Wu et al [35]. As seen in Fig.…”

“…Specifically, smaller bars represent better agreement. Results from previous QM-DFT calculations performed at 0 K (with and without zero-point vibrational energy (ZPE) correction) and 295 K [7,8] are also included as a reference. Of the two non-reactive FFs, COMPASS exhibits the best approximation for the lattice constants, with a total difference smaller than 0.08 Å in each direction.…”

“…Recently, Dri et al [7,8] reported QM-DFT simulations for crystalline cellulose I b in the range of 200 GPa. As shown in Fig.…”

“…crystal structure, defects, percent crystallinity) [3]. Atomistic simulation of cellulose can complement experiments by providing insights into the molecular-scale origins of material properties, some of which cannot be analyzed with current experimental techniques [7,8]. This is particularly true for cellulose nanomaterials whose very small size make it exceedingly challenging to experimentally measure properties [3].…”

“…Dri et al [7,8] predicted the temperature dependence of the crystalline structure, its thermodynamic and elastic properties and anisotropy of cellulose I b , using QM-DFT with a semi-empirical correction for van der Waals interactions [9]. Although recent computational advances enable larger simulation sizes with QM-DFT, the use of MD with classical potential energy functions (force fields) is often necessary to reach the relevant temporal and spatial scales of many research questions [10].…”