Ng. Fazleev et al., POSITRON STATES AND ANNIHILATION CHARACTERISTICS AT THE (100), (110),AND (111) SURFACES OF ALKALI-METALS, Physical review. B, Condensed matter, 57(19), 1998, pp. 12506-12519
In this paper we present results of theoretical studies of pusitron st
ates and annihilation characteristics at the clean surfaces of alkali
metals. Positron surface states and positron work functions have been
computed for the (100), (110), and (111) surfaces of Li, Na, K, Rb, an
d Cs using the modified superimposed-atom method to account for discre
te-lattice effects, and the results are compared with those obtained f
or the transition-metal surfaces. Stable positron surface states are f
ound in all cases, with the Li states lying about 0.5 eV below the bul
k positron band, and other alkali metals having positron surface state
s a few hundredths of an eV below the bulk bands. The results for the
positronium activation energy and positronium work function for the cl
ean surfaces of alkali metals are presented as well. Surface and bulk
state lifetimes and probabilities for a positron trapped in a surface
state to annihilate with relevant core-level electrons are also comput
ed and compared with available experimental data.