Solid-state physical stability

Although solvent-casts cannot be considered as true formulations, their solid state physical stability and dissolution behavior can provide useful information for solid dispersion development. Solvent casting allows components to be accurately dispensed and mixed, and permits the development of rapid, miniaturized, parallel,... 

The inherent problems associated with the computation of the properties of solids have been reduced by a computational technique called Density Functional Theory. This approach to the calculation of the properties of solids again stems from solid-state physics. In Hartree-Fock equations the N electrons need to be specified by 3/V variables, indicating the position of each electron in space. The density functional theory replaces these with just the electron density at a point, specified by just three variables. In the commonest formalism of the theory, due to Kohn and Sham, called the local density approximation (LDA), noninteracting electrons move in an effective potential that is described in terms of a uniform electron gas. Density functional theory is now widely used for many chemical calculations, including the stabilities and bulk properties of solids, as well as defect formation energies and configurations in materials such as silicon, GaN, and Agl. At present, the excited states of solids are not well treated in this way. 

Solid state physical structure appears to be as signincant as chentical constitution in determining the stability of explosives, but apart from crystal structure determination on lower molecular weiglit compounds, such as diaminotrinitro benzene [9] there is little information available on the magnitude of molecular interactions or crysial lattice effects in these remarkable explosives. 

Solid-State Physical Change Mechanism and Stress Stability... 

Solid-state physical change of drug substances is one of the major concerns of pharmaceutical stability due to its potential effects on the drug dissolution rate and bioavailability. Closely related to the mechanism of solid-state chemical reactions [44, 45], the physical changes of crystalline dmg substances may include four steps as described in Fig. 12.4. 

Sveijensky DA, Sahai N (1996) Theoretical prediction of single-site surface protonation equilibrium constants for oxides and silicates in water. Geochim Cosmochim Acta 60 3773-3797 Tasker PW (1979) Stability of ionic crystal surfaces. J Physics C Solid State Physics 12 4977-4984 Toukan K, Rahman A (1985) Molecular-dynamics study of atomic motions in water. Phys Rev B- Con Mat 31 2643-2648... 

Enyashin, A.N. Seifert, G. (2005) Structure, stability and electronic properties of Ti02 nanostructures. Physica Status Solidi B-Basic Solid State Physics, 242,1361-1370. 

---