Origin of the size-dependence of the equilibrium van der Waals binding between nanostructures

Journal Article · Wed Feb 21 00:00:00 EST 2018 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.5018572· OSTI ID:1419407

Tao, Jianmin  ^[1]

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1. Temple Univ., Philadelphia, PA (United States). Dept. of Physics

Nanostructures can be bound together at equilibrium by the van der Waals (vdW) effect, a small but ubiquitous many-body attraction that presents challenges to density functional theory. How does the binding energy depend upon the size or number of atoms in one of a pair of identical nanostructures? To answer this question, we treat each nanostructure properly as a whole object, not as a collection of atoms. Our calculations start from an accurate static dipole polarizability for each considered nanostructure, and an accurate equilibrium center-to-center distance for the pair (the latter from experiment, or from the vdW-DF-cx functional). We consider the competition in each term $$-C_{2k}/d^{2k}$$ ($k=3, 4, 5$) of the long-range vdW series for the interaction energy, between the size dependence of the vdW coefficient $$C_{2k}$$ and that of the $2k$-th power of the center-to-center distance $$d$$. The damping of these vdW terms can be negligible, but in any case it does not affect the size dependence for a given term in the absence of non-vdW binding. To our surprise, the vdW energy can be size-independent for quasi-spherical nanoclusters bound to one another by vdW interaction, even with strong nonadditivity of the vdW coefficient, as demonstrated for fullerenes. We also show that, for low-dimensional systems, the vdW interaction yields the strongest size-dependence, in stark contrast to that of fullerenes. We illustrate this with parallel planar polycyclic aromatic hydrocarbons. Other cases are between, as shown by sodium clusters.

• Research Organization: Temple Univ., Philadelphia, PA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0018194
• OSTI ID: 1419407
• Journal Information: Journal of Chemical Physics, Vol. 148, Issue 7; ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
van der Waals interaction
DFT