Selection of Single-Walled Carbon Nanotubes According to Both Their Diameter and Chirality via Nanotweezers

Diameter- and chirality-dependent interactions between aromatic molecule-based nanotweezers and single-walled carbon nanotubes (SWNTs) are revealed by density functional theory calculations. We found that the threshold diameter of selected SWNTs is determined by the end-to-end distance of the nanotweezer. Large-diameter SWNTs are preferred by a nanotweezer with an obtuse folding angle, whereas small-diameter SWNTs are favored by a nanotweezer with an acute folding angle. The adsorption can be further stabilized by the orientational alignment of the hexagonal rings of the nanotweezer and the SWNT sidewall. Therefore, by taking advantage of the supramolecular recognition ability of the aromatic molecule-based nanotweezer, SWNTs can be enriched with both controllable diameter and chirality.

Linear Jacobi-Legendre expansion of the charge density for machine learning-accelerated electronic structure calculations

Kohn–Sham density functional theory(KS-DFT)is a powerful method to obtain key materials’properties,but the iterative solution of the KS equations is a numerically intensive task,which limits its application to complex systems.To address this issue,machine learning(ML)models can be used as surrogates to find the ground-state charge density and reduce the computational overheads.We develop a grid-centred structural representation,based on Jacobi and Legendre polynomials combined with a linear regression,to accurately learn the converged DFT charge density.This integrates into a ML pipeline that can return any density-dependent observable,including energy and forces,at the quality of a converged DFT calculation,but at a fraction of the computational cost.Fast scanning of energy landscapes and producing starting densities for the DFT self-consistent cycle are among the applications of our scheme.

Purely one-dimensional ferroelectricity and antiferroelectricity from van der Waals niobium oxide trihalides

Intrinsic one-dimensional(1D)ferroelectric materials are rarely reported but are highly sought to break the size limit of nanostructured conventional ferroelectrics.Herein,we report a class of inborn 1D ferroelectric nanowires,namely 1D NbOX_(3)(X=Cl,Br,and I),that can be directly obtained from experimentally realized van der Waals crystals.In addition to the sizable spontaneous polarization,1D NbOX_(3) exhibits low ferroelectric switching barriers,small coercive electric fields,and high critical temperature,governed by the hybridization of the Nb empty d orbitals and the O p orbitals(d^(0) rule).Moreover,the double-channel structure of 1D NbOX_(3) also enables the emergence of 1D antiferroelectric metastable states.Our findings not only propose a class of 1D ferroelectric materials toward the development of miniaturized and high-density electronic devices,but also pave an avenue of obtaining intrinsic 1D ferroelectrics from van der Waals crystals.