The D-DIA or deformation-DIA is an apparatus used for high pressure and high temperature deformation experiments. The advantage of this apparatus is the ability to apply pressures up to approximately 15 GPa while independently creating uniaxial strains up to 50%. Theory The D-DIA utilizes the same principle that other high pressure apparatuses (such as the diamond anvil cell) use to create elevated pressure on a specimen. Pressure = Force/area By generating a force, in the case of the D-DIA through a hydraulic ram, a greater force can then be applied to the sample by decreasing the area of the anvils on the end that are in contact with the sample assembly. Design The D-DIA is based on the similar DIA, which is a cubic-anvil apparatus. The D-DIA is a type of multi-anvil deformation apparatus that uses 6 cubically arranged anvils to provide independent pressurization and deformation of the sample. Four anvils of the cubic arrangement are oriented in the horizontal opposing at 90°, and the remaining two anvils are oriented in the vertical within two guide blocks. The back side of each horizontal anvil comprises two faces of a virtual octahedron. By the symmetry imposed from the advancing guide blocks and anvils, all axes of the virtual octahedron are then strained equally and thus provide hydrostatic pressure to the sample. In order to create a deviatoric stress, oil is pumped using two differential rams behind the top and bottom anvils located within the guide blocks allowing them to advance independent of the other four. By advancing just one anvil pair, a deviatoric stress is created thus altering the previously cubic stress field to one that is tetragonal. The induced flow is approximately axially-symmetric with respect to the cylindrical sample). By advancing an anvil pair pressure would begin to increase on the sample as deformation progresses, but the D-DIA has the capability of bleeding off oil from the main ram (which engages the guide blocks) while advancing the differential pumps, in order to maintain a constant sample pressure during deformation. Sample assembly There are multiple designs of sample assemblies that are currently used in the D-DIA. The various sample assembly designs use different materials in their construction to accomplish different goals, but all contain the same common elements: internal resistive heater, pressure medium and upper/lower pistons. The overall shape of the sample assembly is a cube (typically around 6mm), this shape