Mechanically modulated electronic properties of water-filled fullerenes
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Mechanically modulated electronic properties of water-filled fullerenes K. Min, A. Barati Farimani, 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 61802, USA Address all correspondence K. Min at [email protected] (Received 28 October 2014; accepted 20 April 2015)
Abstract We report on electronic properties of water-filled fullerenes [H2O(n)@C60, H2O(n)@C180, and H2O(n)@C240] under mechanical deformation using density functional theory. Under a point load, energy gap change of empty and water-filled fullerenes is investigated. For C60 and H2O(n) @C60, the energy gap decreases as the tensile strain increases. For H2O(n)@C60, under compression, the energy gap decreases monotonously while for C60, it first decreases and then increases. Similar behavior is observed for other empty (C180 and C240) and water-filled [H2O(n) @C180 and H2O(n)@C240] fullerenes. The energy gap decrease of water-filled fullerenes is due to the increased interaction between water and carbon wall under deformation.
Introduction The encapsulation of a single water molecule, nitrogen, hydrogen, and other molecules/atoms in a C60 opens up new opportunities for designing new nanoscale devices.[1–3] The endohedral fullerenes have different structural and mechanical properties compared with empty fullerenes. Pupysheva et al. showed that a buckyball can be used for storage of multiple hydrogen molecules.[3] Shen studied the effect of having Si and Ge inside C60 on the mechanical response under compression.[4] In our previous study, we have investigated the mechanical properties of water-filled C60.[5] It has recently been shown that the rotational diffusion and entropy of a single water molecule inside C60 is an order of magnitude higher compared with the bulk molecule.[6] The electronic properties of C60 can be highly affected from the interaction with molecules. Rivelino et al. studied C60 and hydrated C60 using Monte Carlo/density functional theory (DFT) and showed that the electronic properties (specifically, energy gap) change due to the interaction between C60 and outside water molecules.[7] Kawahara et al. showed that the density of states (DOS) of C60 can be significantly modified when deposited on Cr(001) surface.[8] It is noteworthy that mechanical deformation can also significantly affect the electronic properties of nano materials. In a relevant study, Ni et al. showed that the uniaxial tension of graphene can open a band gap of about 300 meV.[9] Similar study was done by Yang et al. for carbon nanotubes (CNT), and they demonstrated that the uniaxial and torsional deformation can modify the band gap of CNT.[10] Mechanically induced electronic changes in nano structures can enable the design of novel electronic devices such as bio-sensors and field effect transistors (FETs).[9–11] Scalise et al. showed that the semiconducting to
metallic transition of MoS2 occurs when a compressive or tensile deformatio
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