The class of hexagonal close packed (HCP) metals, such as Mg and Ti, can provide a potential solution to the ever-increasing portfolio of structural applications that require advanced materials with unprecedented combinations of mechanical properties. Successful incorporation of HCP metals into engineering designs is, however, hindered by their limited plasticity. Recent results have introduced the exciting potential of "twin mesh engineering" to overcome the long-standing problem of simultaneous strengthening and toughening in HCP metals. Designing for twin meshes, however, poses interesting challenges since the parameter space is vast and highly scale dependent. This program aims to explore, staring with first principles, the effect of changes in chemical composition via alloying additions on the energetics of slip and relative differences among the barriers to activate the multitude of slip modes in HCP alloys. The integrated experimental and modeling research activities seek to answer: Can alloying be used to make the "right" twin for high strength, high toughness (HSHT) HCP alloys? The DMREF program is a collaborative research program between the University of California at Santa Barbara (UCSB), at Irvine (UCI) and at Davis (UCD).