  A disclination in a hexatic membrane favors the development of Gaussian
curvature localized near its core. The resulting global structure of the
membrane has mean curvature, which is disfavored by curvature energy. Thus a
membrane with an isolated disclination undergoes a buckling transition from a
flat to a buckled state as the ratio $\kappa/K_{A}$ of the bending rigidity
$\kappa$ to the hexatic rigidity $K_{A}$ is decreased. In this paper we
calculate the buckling transition and the energy of both a positive and a
negative disclination. A negative disclination has a larger energy and a
smaller critical value of $\kappa/K_{A}$ at buckling than does a positive
disclination. We use our results to obtain a crude estimate of the
Kosterlitz-Thouless transition temperature in a membrane. This estimate is
higher than the transition temperature recently obtained by the authors in a
renormalization calculation.
