Technetium incorporation in scheelite: insights from first-principles

Area of Science:

• Materials Science
• Nuclear Chemistry
• Computational Chemistry

Background:

• Scheelite (CaWO₄) is a mineral relevant to nuclear waste management and forensics.
• Understanding the behavior of technetium-99 (⁹⁹Tc) in crystalline structures is crucial for nuclear applications.
• Previous studies have explored CaWO₄ properties, but detailed atomistic insights into ⁹⁹Tc incorporation were limited.

Purpose of the Study:

• To perform atomistic investigations of ⁹⁹Tc incorporation in scheelite (CaWO₄) using density functional theory (DFT).
• To predict energetically favorable sites for ⁹⁹Tc doping within the CaWO₄ lattice.
• To simulate X-ray diffraction (XRD) patterns for different ⁹⁹Tc defect types to aid experimental interpretation.

Main Methods:

• Density functional theory (DFT) calculations were employed for atomistic simulations.
• Lattice constants, bulk modulus, and volume compression of CaWO₄ were calculated and compared with experimental data.
• Defect formation energies were computed for various interstitial and substitutional sites of ⁹⁹Tc in CaWO₄.
• X-ray diffraction (XRD) spectra were simulated for different ⁹⁹Tc defect configurations.

Main Results:

• Calculated lattice constants and bulk modulus for CaWO₄ showed good agreement with experimental values.
• Both interstitial (I(O_h)) and substitutional (S(W)) sites were identified as energetically favorable for ⁹⁹Tc doping in CaWO₄.
• Simulated XRD spectra provide potential signatures for identifying ⁹⁹Tc incorporation in experimental data.

Conclusions:

• The study successfully predicted favorable sites for ⁹⁹Tc doping in scheelite using DFT.
• The findings offer insights into materials potentially generated during nuclear weapons testing.
• Simulated XRD patterns can serve as valuable spectral signatures for nuclear forensics applications.