A method for determining the ability of a cement composition to withstand subterranean formation conditions comprising obtaining an experimental diffraction pattern of the cement composition, generating a theoretical diffraction pattern of the cement composition, comparing the experimental diffraction pattern with the theoretical diffraction pattern, refining the theoretical diffraction pattern using a structural refinement method, determining the relative fraction of the crystalline phases present in the cement composition from the theoretical diffraction pattern, and determining the ability of the cement composition to withstand subterranean formation conditions. A method for determining the ability of a cement composition to withstand subterranean formation conditions comprising obtaining an experimental diffraction pattern of the cement composition, generating a theoretical diffraction pattern of the cement composition, comparing the experimental diffraction pattern with the theoretical diffraction pattern, refining the theoretical diffraction pattern using a structural refinement method, wherein the structural refinement method provides both crystallographic data and compositional data related to the cement composition, and determining the ability of the cement composition to withstand subterranean formation conditions by evaluating the crystallographic data and compositional data.