Solid State Phenomena Vol. 373

Abstract: We investigate the hole formalism and positron screening within the framework of Den sity Functional Theory (DFT). This study revisits the Local Density Approximation (LDA) and its extensions - such as semilocal functionals and the Weighted Density Approximation (WDA), show ing their importance in modeling exchange and correlation potentials. We further examine the two-component density functional approach to describe electron-positron interactions, with particular em phasis on the formation of the electron screening cloud around the positron site. The performance of various computational techniques in describing charge inhomogeneities and positron surface states is critically assessed. Moreover, we identify the limitations of conventional models in low-dimensional systems and propose a novel method based on the electronic dielectric response to improve the accu racy of positron screening predictions.

Abstract: The development of algorithms and simulation codes as well as the ever increasing comput ing power available have have enabled many-body simulations to emerge as a viable alternative to the two-component density-functional theory to study positron states and annihilation in solids, defects and on solid surfaces. One practical many-body method is quantum Monte Carlo. This article will aim to present the practitioners of positron annihilation methods the basic ideas of the variational and diffusion quantum Monte Carlo, provide examples of their past and recent applications in positron physics of atomic/molecular and solid-state systems as well as an outlook into the future.