The dependence of the GaP and InP(0 0 1) surface reconstructions on the che
mical potentials of their constituents is explored. Based on first-principl
es pseudopotential plane-wave calculations the surface phase diagram is obt
ained. For both GaP(0 0 1) and Inp(0 0 1) surfaces, P-top dimer reconstruct
ions are predicted for P-rich conditions, while for group III-element rich
preparations a mixed dimer (III-P) on a complete III-layer is favoured. For
GaP, in addition, a Ga-top dimer reconstruction seems to be a possibility
for very Gallium rich growth conditions. STM images are calculated in order
to contribute to a solution of the structural puzzle. (C) 2001 Published b
y Elsevier Science B.V.