  Total Routhian Surface (TRS) calculations have been performed to investigate
shape coexistence and evolution in neutron-deficient krypton isotopes
${}^{72,74,76}$Kr. The ground-state shape is found to change from oblate in
${}^{72}$Kr to prolate in ${}^{74,76}$Kr, in agreement with experimental data.
Quadrupole deformations of the ground states and coexisting $0^{+}_{2}$ states
as well as excitation energies of the latter are also well reproduced. While
the general agreement between calculated moments of inertia and those deduced
from observed spectra confirms the prolate nature of the low-lying yrast states
of all three isotopes (except the ground state of ${}^{72}$Kr), the deviation
at low spins suggests significant shape mixing. The role of triaxiality in
describing shape coexistence and evolution in these nuclei is finally
discussed.
