<i>Ab initio</i>study of positron trapping at a vacancy in GaAs

Gilgien, L.; Galli, Giulia; Gygi, François; Car, Roberto

doi:10.1103/physrevlett.72.3214

Cited by 66 publications

(52 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…12 The enhancement factor in the Boroński-Nieminen twocomponent formalism 6 is based on the results of the manybody calculations by Lantto. 30 Gilgien et al 11 and Barbiellini et al 26,27 have used the n + → 0 limit parametrizations consistent with the correlation energy results of Arponen and Pajanne. 28 The LDA systematically underestimates positron lifetimes in materials because it overestimates the annihilation with core electrons for which the correlation effects are less important.…”

Section: B Annihilation Rate Modelsmentioning

confidence: 92%

Modeling the momentum distributions of annihilating electron-positron pairs in solids

2006

View full text Add to dashboard Cite

Measuring the Doppler broadening of the positron annihilation radiation or the angular correlation between the two annihilation gamma quanta reflects the momentum distribution of electrons seen by positrons in the material. Vacancy-type defects in solids localize positrons and the measured spectra are sensitive to the detailed chemical and geometric environments of the defects. However, the measured information is indirect and when using it in defect identification comparisons with theoretically predicted spectra is indispensable. In this article we present a computational scheme for calculating momentum distributions of electron-positron pairs annihilating in solids. Valence electron states and their interaction with ion cores are described using the all-electron projector augmented-wave method, and atomic orbitals are used to describe the core states. We apply our numerical scheme to selected systems and compare three different enhancement ͑electron-positron correlation͒ schemes previously used in the calculation of momentum distributions of annihilating electron-positron pairs within the density-functional theory. We show that the use of a state-dependent enhancement scheme leads to better results than a position-dependent enhancement factor in the case of ratios of Doppler spectra between different systems. Further, we demonstrate the applicability of our scheme for studying vacancy-type defects in metals and semiconductors. Especially we study the effect of forces due to a positron localized at a vacancytype defect on the ionic relaxations.

show abstract

Section: B Annihilation Rate Modelsmentioning

confidence: 92%

Modeling the momentum distributions of annihilating electron-positron pairs in solids

2006

View full text Add to dashboard Cite

show abstract

“…For defects in semiconductors, calculations optimizing the electronic and ionic structures, as well as the positron density within the 2CDFT, have appeared. [22][23][24][25][26] In the present work, we apply the so-called conventional scheme in which ͑i͒ the localized positron density does not directly affect the average DFT electron density ͑the positron and its screening electron cloud form a neutral quasiparticle entering the system͒ and ͑ii͒ the positron state and annihilation characteristics are calculated in the LDA and at the zeropositron-density limit of the electron-positron correlation functionals. For example, this means that the potential entering the single-particle equation for the positron state + ͑r͒ reads as…”

Section: A Theoretical Modelsmentioning

confidence: 99%

Energetics of positron states trapped at vacancies in solids

Makkonen

Puska

2007

Phys. Rev. B

View full text Add to dashboard Cite

We report a computational first-principles study of positron trapping at vacancy defects in metals and semiconductors. The main emphasis is on the energetics of the trapping process including the interplay between the positron state and the defect's ionic structure and on the ensuing annihilation characteristics of the trapped state. For vacancies in covalent semiconductors the ion relaxation is a crucial part of the positron trapping process enabling the localization of the positron state. However, positron trapping does not strongly affect the characteristic features of the electronic structure, e.g., the ionization levels change only moderately. Also, in the case of metal vacancies, the positron-induced ion relaxation has a noticeable effect on the calculated positron lifetime and momentum distribution of annihilating electron-positron pairs.

show abstract

“…Only recently have there appeared a few calculations using the full TCDFT. 3,4,16 Instead of the twocomponent schemes the so-called conventional scheme has been widely used for localized positron states. In the conventional scheme localized positron states are calculated with the same procedure as the delocalized ones.…”

Section: ͑4͒mentioning

confidence: 99%

“…This is a rather small relaxation compared to semiconductors, for which the open lattice structure and different possibilities of covalent bond formation give a large freedom for the ionic rearrangements around vacancies. 4,3 The small inward relaxation should shorten the positron lifetimes for metal vacancies. This can bring the positron lifetimes, or the v / b ratios, calculated using the self-consistent electronic structures into agreement with the experiment, but it worsens the agreement in the case of the AT-SUP method.…”

Section: Fig 2 Calculated Positron Lifetimes For the Cu Vacancy As mentioning

confidence: 99%

“…Recently, there have been a few calculations for positron states at vacancies in semiconductors employing state-of-the-art electronic-structure methods and the TCDFT. [3][4][5] In this work our aim is to raise the status of the calculations of the positron annihilation characteristics for metals and to provide calculated benchmarks for positron lifetimes at vacancies in metals.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

First-principles calculation of positron annihilation characteristics at metal vacancies

1996

View full text Add to dashboard Cite

Annihilation characteristics for positrons trapped at metal vacancies are calculated from first principles. The calculations are based on different implementations of the two-component density-functional theory, and different numerical methods to solve the ensuing Kohn-Sham equations have been employed. The convergence of the positron annihilation characteristics calculated within different schemes is discussed, and the positron lifetimes obtained are compared with experiment. ͓S0163-1829͑96͒07145-7͔

show abstract

Ab initiostudy of positron trapping at a vacancy in GaAs

Cited by 66 publications

References 19 publications

Modeling the momentum distributions of annihilating electron-positron pairs in solids

Modeling the momentum distributions of annihilating electron-positron pairs in solids

Energetics of positron states trapped at vacancies in solids

First-principles calculation of positron annihilation characteristics at metal vacancies

Contact Info

Product

Resources

About