Proposed Parameter-Free Model for Interpreting the Measured Positron Annihilation Spectra of Materials Using a Generalized Gradient Approximation

Abstract

Positron annihilation spectroscopy is often used to analyze the local electronic structure of materials of technological interest. Reliable theoretical tools are crucial to interpret the measured spectra. Here, we propose a parameter-free gradient correction scheme for a local-density approximation obtained from high quality quantum Monte Carlo data. The results of our calculations compare favorably with positron affinity and lifetime measurements opening new avenues for highly precise and advanced positron characterization of materials.

Two-Component Density Functional Study of Positron-Vacancy Interaction in Metals and Semiconductors

“…Perhaps, these are oversimplifications. To remove these drawbacks, one possible solution is applying the GGA to the positronrelated terms in the calculation [16,17]. Unfortunately, a TC version of the positron GGA has not yet been established.…”

Experimental and theoretical cross sections for positron scattering from the pentane isomers

“…Given that our IAM-SCAR formalism may not be so accurate at incident energies below 30 eV or so, ab initio positron-molecule calculations, such as those based on density functional theory (DFT) or self-consistent field with configuration interaction (SCF-CI), might be more precise at those very low energies. In particular, we acknowledge the recent fundamental improvements in the electron-positron scattering potential within the DFT framework, both in the local density approximation (LDA) (Drummond et al, 2011) and the generalized gradient approximation (GGA) (Barbiellini and Kuriplach, 2015) methods. Although these theoretical approaches do not explicitly account for Ps formation, which is an important scattering channel at such low energies, they might lead to a clearer picture of the isomer effect.…”

Application of the weighted-density approximation to the accurate description of electron-positron correlation effects in materials

“…Here we consider a set of elemental bulk materials for which experimental positron-annihilation lifetimes are available 48 . Table II gives the experimental and LDA lifetimes, obtained with the Brandt-Reinheimer (BR) expression 28,49,50 , the Boronski-Nieminen (BN) parametrization 19 and the Drummond (Dr) parametrization 31 of the LDA.…”

“…In fact, the GGA correction to the LDA positron correlation potential is derived from a gradient correction to the induced contact charge density 53 ∆n GGA e (r p |r p ) = ∆n LDA e (r p |r p )e −α (rp) , (25) with = |∇n e | 2 /q 2 T F , where 1/q T F is the Thomas-Fermi screening length. The parameter α can be chosen phenomenologically 53,54 , though recently a connection with the LDA potential was found 48 .…”