LEED I(V)

LEED I(V) — also sometimes referred to as LEED I(E) — is the quantitative analysis of energy-dependent low-energy electron diffraction (LEED) patterns. It involves the acquisition of LEED patterns as a function of the energy of the electron beam — usually referred to as “LEED videos” or “LEED movies”. The intensity of each “spot” is then extracted to obtain so-called I(V) curves — sometimes also referred to as spectra. Such I(V) curves are exceptionally sensitive to the precise position, vibrational amplitude, and chemical element of each atom in the surface unit cell. I(V) curves can also be calculated based on a test structural model of the surface. Comparing calculated and experimental I(V) curves allows one to accept or discard structural models for surfaces with picometre-level accuracy.

For a detailed introduction on the theory and applications of LEED and LEED I(V) we suggest, for example, Chapter 4 in Fauster et al. [4] or the overview by Heinz [5].

In essence, the goal of a LEED-I(V) calculation is the determination of energy-dependent electron-scattering amplitudes and of the corresponding intensities of diffracted electron beams. In ViPErLEED, LEED-I(V) calculations are performed by the viperleed.calc Python package, which acts as a comprehensive wrapper and major feature extension to the established TensErLEED program package. Based on the input structure and the desired calculation parameters, ViPErLEED can calculate the LEED-I(V) spectra for a given surface structure (see also Reference calculation), compare these to experimental data (see also \(R\)-factor calculation), and perform a structure optimization (see Structure search) using the tensor-LEED approach.

For computational details, have a look at the relevant ViPErLEED paper [3] and at the original work describing TensErLEED by Blum and Heinz [6].