A First Principles Simulation Framework for the Interactions between a Si(001) Surface and a Scanning Probe

Abstract

By means of total energy calculations within the framework of the local density approximation (LDA), the interactions between a silicon Si(001) surface and a scanning probe are investigated. The tip of the probe, comprising 4 Si atoms scans along the dimer lines above an asymmetric p(2 × 1) surface, at a distance where the chemical interaction between tip-surface is dominant and responsible for image resolution. At that distance, the tip causes the dimer to toggle when it scans above the lower atom of a dimer. The toggled dimers create an alternating pattern, where the immediately adjacent neighbours of a toggled dimer remain unchanged. After the tip has fully scanned across the p(2 × 1) surface, causes the dimers to arrange in a p(2 × 2) reconstruction, reproducing the images obtained in scanning probe experiments. Our modelling methodology includes simulations that reveal the energy input required to overcome the barrier to the onset of dimer toggling. The results show that the energy input to overcome this barrier is lower for the p(2 × 1) surface than that for the p(2 × 2) or c(4 × 2) surfaces

Plastic bending in a semiconducting coordination polymer crystal enabled by delamination

“…Such delamination in the bent sections undoubtedly affects the deformed local structures 39 , 40 . Due to such different interaction strengths, significant anisotropy is also found in Young’s modulus, linear compressibility, and shear modulus (Supplementary Figs 3 – 6 , Supplementary Tables 1 – 2 ) via density functional theory (DFT) calculations 41 – 43 . Further discussion on these properties can be found in Supplementary Note 1 .…”