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Structure and Dynamics of Water Confined in a Boron Nitride Nanotube Chang Y. Won and N. R. Aluru*

Summary: Structure and Dynamics of Water Confined in a Boron Nitride Nanotube
Chang Y. Won and N. R. Aluru*
Department of Mechanical Science and Engineering, Beckman Institute for AdVanced Science and Technology,
UniVersity of Illinois at Urbana-Champaign, Urbana, Illinois 61801
ReceiVed: August 22, 2007; In Final Form: October 23, 2007
Recent molecular dynamics simulations have shown that a finite-length (5,5) boron nitride nanotube (BNNT)
in contact with an aqueous reservoir has superior water permeation properties compared to a (5,5) carbon
nanotube of similar diameter and length. In this work, by using density functional theory (DFT), we compute
the electrostatic potential arising from the weak ionic and covalent bonding of B-N. Quantum partial charges
of B and N atoms, determined by matching the electrostatic potential computed by the DFT, are then included
in molecular dynamics simulations to investigate the structure and dynamics of water confined in BNNTs of
sizes ranging from (5,5) to (10,10). When partial charges are included, we observe that the wetting behavior
of the (5,5) BNNT has improved and the single-file water chain in both (5,5) and (6,6) BNNTs has an L-defect.
Further, with partial charges, except for a (9,9) BNNT which exhibits anomalous behavior, the diffusion
coefficient of confined water molecules in (5,5), (6,6), and (10,10) BNNTs is found to decrease due to the
formation of a hydrogen bond between water and nitrogen atoms. For a (9,9) BNNT, in the absence of partial
charges, an ice-shell structure was observed with a critical slowing in the diffusion coefficient. When partial
charges are included, the diffusion coefficient is found to increase because of the presence of an additional
single-file water chain inside the ice-shell structure.
1. Introduction


Source: Aluru, Narayana R. - Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign


Collections: Engineering; Materials Science