Radioparagenesis: The formation of novel compounds and crystalline structures via radioactive decay

Abstract

When a crystalline material is made with radioactive isotopes, the structure of that material will change as the radioisotope decays. Using density functional theory, we explore the potential structures formed from this decay, a process we term radioparagenesis. Using three systems as examples – CsCl, SrO, and Lu₂O₃ – we describe how in each case a here-to-fore unobserved crystalline phase of BaCl, ZrO, and Hf₂O₃ can be formed, resulting in novel crystalline materials. We examine how the formation of these phases depends on the parent structure and the pathways available to the system upon the decay of the radioisotope. We discuss the implications of this phenomenon for the formation of new materials.

Keywords:

• transmutation
• crystal structure
• density-functional theory
• radiation effects
• computer modeling
• phase transformations
• phase stability

Acknowledgements

The authors thank J. Gale and A.F. Voter for helpful discussions. Work at LANL was sponsored by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering. Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by Los Alamos National Security, LLC, for the National Nuclear Security Administration of the U.S. Department of Energy under contract DE-AC52-06NA25396.

Notes

Notes

1. VASP does not have an LDA pseudopotential for Lu. Thus, we had to calculate the bandgap change for Lu₂O₃ with GGA. However, we expect that the qualitative change in bandgap would be similar for LDA.

2. During β⁻ decay, β⁻ particles are emitted with kinetic energies varying from 0 to near the Q value of the disintegration reaction. The energy distribution of these β⁻ particles is bell-shaped (asymmetric) and peaks at ∼Q/3. This is the “most probable” β⁻ particle energy.