Electron-positron momentum density distribution in diamond

• Published in: Applied surface science Vol. 116; pp. 330 - 334
• Main Authors: Nilen, R.W.N., Connell, S.H., Schmidt, W.G., Britton, D.T., Verwoerd, W.S., Sellschop, J.P.F., Shrivastava, S.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.1997; Elsevier Science
• Subjects: Ab initio pseudopotential; Calculation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Diamond; Doppler broadening; Electron states; Exact sciences and technology; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other interactions of matter with particles and radiation; Physics; Positron annihilation; Positron states; 71.60; Doppler broadening; Ab initio pseudopotential; 78.70.B; 71.15.M; Diamond; Calculation; Momentum distribution; Annihilation; Positron probes; Diamonds; Property structure relationship; Doppler effect; Experimental study
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/S0169-4332(96)01078-1

We have measured the momentum distribution of the electron-positron annihilating pair in diamond as a function of crystallographic orientation, using the Doppler broadening technique of positron annihilation spectroscopy. A 1% variation in the longitudinal projection of the momentum distribution was observed as the sample was rotated about the 〈110〉 axis. This anisotropic distribution shows an excellent agreement with a theoretical calculation performed based on two component density functional theory in the local density approximation. The results suggest strongly that the bulk positron density, though delocalized and inhomogeneous, has sufficient amplitude at the intra-bond regions such that the annihilation characteristics are dominated by the bond electron density and momentum distribution.