We investigate the ground state properties of proton-rich nuclei in the fra
mework of the relativistic mean-field model. Calculations show that the exp
erimental proton halo in the nuclei P-26,P-27,P-28 can be reproduced by the
model. The proton halos can appear in proton-rich nuclei because the total
nuclear potential is attractive up to the radial distance r approximate to
5.5 fm. But the size of proton halos is finite due to the limitation of th
e Coulomb potential barrier. The mean-square radius of a halo proton is not
very sensitive to the separation energy of the last proton in some very pr
oton-rich nuclei due to the effect of the Coulomb barrier. This behavior is
different from the case of a neutron halo where the mean-square radius of
a halo neutron is inversely proportional to the separation energy of the la
st halo neutron. We have also analysed the differences of the relativistic
mean-field potentials of Al-25 and P-26 and found that the isovector potent
ial from the rho meson has an important effect on the differences. (C) 1999
Elsevier Science B.V. All rights reserved.