High-energy beams of X-rays used in studies of molecular structure typically have imperfect wavefront quality. Improved point-spread functions can in principle be made by adjustment of a deformable mirror (DM) in the beam train. Conventional DMs are unsuitable because they are not intended for use at the necessary grazing incidence angles, and the optical surface is not sufficiently stable. We describe the conceptual design for a new DM that addresses the requirements of this application. Our design draws on successful strategies employed in the adaptive secondary mirrors at the MMT and LBT telescopes, including the use of voice-coil actuators with collocated capacitive position sensors.