Calculation of images of orientedC60molecules using molecular orbital theory

Abstract

Using Hückel molecular-orbital theory, images are created to represent the electron distributions expected for a C 60 molecule adsorbed on a substrate. Three different orientations of the C 60 molecule on the substrate are considered. The effect of the interaction of the molecule with the substrate is treated purely from the basis of symmetry using group theoretical methods. The resulting electron distributions are then used to generate idealized images which represent how the molecule may appear when observed in a scanning tunneling microscope ͑STM͒ experiment. Comparison is made with STM images appearing in the literature. It is found that the more complicated ab initio methods usually employed to simulate STM images are not required in order to match observed results. Furthermore, we find that an unequivocal identification of the orbitals responsible for a given STM image cannot be made from analysis of the STM image alone.

Visualization of static Jahn-Teller effects in the fullerene anionC60−

“…We took a similar approach in a recent paper relating to neutral C 60 molecules adsorbed onto a surface ͑where JT effects can be ignored͒, where we modeled the HOMO, LUMO, and LUMO+ 1. 5 We obtained simulated STM images that are almost identical to those obtained using DFT. The work in this paper amplifies upon the first steps made to incorporate the JT effect into the LUMO that was taken in Ref.…”

“…Rather, we use parameters ͑e.g., high- tunneling current, arbitrarily sharp STM tip, etc.͒ that produce images that give a good "picture" of the electron density responsible for the image. 5,23 Thus, our images should be thought of as representing the optimum possible image quality that could be recorded using STM. It is always possible to downgrade these high-resolution images.…”

“…This degeneracy cannot be maintained on the surface as inversion symmetry must be necessarily absent. In a recent paper, 5 the effects of the loss of degeneracy due to surface adsorption on the appearance of the molecule, as observed using STM, were explored theoretically. Various images were inferred, several of which compare very well with features observed in actual STM work.…”

Strong spin-filtering and spin-valve effects in a molecular V–C60–V contact

“…This points to a charge transfer from the V atoms to the C 60 leaving the d zx / d yz orbital energies closest to E F . Since the d zx / d yz orbitals match the symmetry with angular momentum m = 1 for rotation around the V–C 60 –V axis of the pentagon-prone 3-fold degenerate LUMO states (t 1 u symmetry [33–34]), we can expect the observed orbitals in the transport channels. For minority spins d zx and d yz orbitals are almost empty and shifted away from E F , resulting in a vanishing transmission.…”

Engineering Negative Differential Conductance with the Cu(111) Surface State

“…When the molecule is adsorbed on a surface these degeneracies will be reduced [27], and, importantly here, the orbital angular momentum components onto the common symmetry axis perpendicular to the surface will depend on the molecular orientation. In Tab.…”