The electromechanical response of hexagonal-boron nitride nanosheets (h-BNSs) was studied via molecular dynamics simulations (MDS) with a three-body Tersoff potential force field using a charge-dipole (C-D) potential model. Carbon (C)-doped h-BNSs with triangular, trapezoidal and circular pores were considered. The elastic and piezoelectric coefficients of h-BNSs under tension and shear loading conditions were determined. The induced polarization in h-BNSs was found to depend on the local arrangement of C atoms around B and N atoms, and the polarization increases if C atoms are surrounded by N atoms. This is attributed to the generation of higher dipole moments due to C–N bonds compared with C–B bonds. At ∼5.5% C-doping concentration, the axial piezoelectric coefficient of doped h-BNSs with triangular and trapezoidal pores increased by 18.5% and 3.5%, respectively, while it reduced by 22.5% in the case of circular pores compared to pristine h-BNS. The shear piezoelectric coefficient of C-doped h-BNSs with triangular and trapezoidal pores increased by 20.5% and 1%, respectively, while it reduced by 7% in case of circular pores. Young’s moduli of C-doped h-BNSs with triangular, trapezoidal and circular pores increased by 9%, 7.5% and 5.5%, respectively, due to the C–C bonds being stronger than all other bonds. The respective improvements in shear moduli are 8.5%, 5% and 5%. The elastic and piezoelectric properties of armchair h-BNSs were found to be higher than zigzag h-BNSs. The results also reveal that the piezoelectric coefficient increases as doping increases; it reaches its maximum value around 0.41 C m−2 at 12.6% C-doping concentration and then starts decreasing. The present work shows that we can engineer the electromechanical response of h-BNSs via novel pathways such as different types and size of pores as well as C-doping concentration to suit a particular nanoelectromechanical systems (NEMS) application.
The hydrogen adsorption and desorption capacity of polycrystalline graphene sheets (PGs) with and without titanium (Ti) decoration is investigated using molecular dynamics simulations. Interatomic interactions of PGs are modeled using Tersoff potential, and the remainder of interactions are calculated via Lennard-Jones potential. The effect of grain size and Ti concentration on the mechanical properties and hydrogen adsorption capacity of PGs is studied. The presence of grain boundaries in PGs reduces their mechanical properties, while the decoration of Ti adatoms does not significantly alter the mechanical properties of PGs. PGs showed a ~ 57% increase in the gravimetric density of H 2 at 300 K and 50 bar compared to the pristine graphene sheet. At 100 bar pressure, PGs with 1% Ti concentration achieved a gravimetric density of 9.9 wt.% and 3.2 wt.% at 77 and 300 K, respectively. In Ti-decorated PGs, the desorption curve follows the same path at 300 K as the adsorption curve with increasing Ti concentration, and the desorption curve diverges from the adsorption curve after 1.5% Ti concentration at 77 K. The potential use of the isosteric enthalpy of adsorption to determine the adsorbent's capability for adsorbing H 2 molecules is also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.