Density-functional theory is used to calculate unit-cell energies of $\alpha \text{-Pu}$ and $\delta \text{-Pu}$ lattices containing point defects that are manifest in terms of a contaminant He atom. These cell energies are used in the development of a new $\text{exp}-6$ Pu-He interatomic potential. Molecular-dynamics simulations are conducted to investigate the dynamics of individual He atoms and of a cluster of He atoms in a $\delta \text{-Pu}$ lattice. In both cases, the He atoms are shown to precipitate chain reactions involving split interstitial migration of Pu. The rate of this split interstitial migration is calculated. Molecular dynamics is also used to investigate the dynamics of an isolated He bubble in a $\delta \text{-Pu}$ lattice. Questions concerning the stability of a He bubble possessing a He-to-vacancy ratio of 3:1 are investigated. Molecular-dynamics simulations investigating the evolution of bubble shape over time are carried out.

Results obtained by two methods for the measurement of the sound velocity in tim samples (initial density of 7.28 g/cm³ and impurities less than 0.085%) are presented. In the range of pressures from 30 to 150 GPa, the sound velocity is determined by the overtake method with the use of indicator liquids. The luminescence of the indicator liquids is detected by photodiode-based optical gauges. At shock compression pressures of 5–18 GPa, the sound velocity in tin is measured by the counter release method with the use of manganin-based gauges. The experimental data are compared with numerical predictions and results of other authors. The boundaries of the tin melting region on the shock adiabat are found.

Cerium has a complex phase diagram that is explained by the presence of structural phase transitions. Experiments to measure the sound velocities in cerium by two methods were carried out to determine the onset of cerium melting on the Hugoniot. In the pressure range 4–37 GPa, the sound velocity in cerium samples was measured by the counter release method using manganin-based piezoresistive gauges. In the pressure range 35–140 GPa, the sound velocity in cerium was measured by the overtaking release method using carbogal and tetrachloromethane indicator liquids. The samples were loaded with plane shock wave generators using powerful explosive charges. The onset of cerium melting on the Hugoniot at a pressure of about 13 GPa has been ascertained from the measured elastic longitudinal and bulk sound velocities.

The perturbation method is employed in an experimental‐numerical study of the behavior of Ta subjected to both shock and shockless (approximately quasi‐isentropic) loading. The loading produces large deformation plastic flow, pressures on the order of 10–80 GPa, and strain rates on the order of ${10}^5{\text{–10}}^9\hspace{0.17em}{\mathrm{s}}^{\text{−1}}.$ Metallographic analysis is used to assess microstructural changes. Perturbation growth is reasonably well predicted with the use of a finite element continuum code and the Steinberg‐Glushak model. Perturbation growth in Ta is compared to that of Al and Cu. Observations are made concerning fundamental differences in the behavior of fcc versus bcc materials subjected to the studied load environment. Ramifications of these differences on model development is discussed.

The capabilities of a recently-developed continuum-level model developed for the purpose of predicting the evolution of spall, including the compaction of damaged material, and applicable to the formation of spall in the material that is fully solid as well as material that is locally liquid, are evaluated against empirical data for lead. The model accounts for inertial forces, elastoplastic constitutive behavior, viscosity, and surface tension. Predictions of spall layer thickness are shown to match the empirical data reasonably well.