Electronic, mechanical, and thermodynamic properties of americium dioxide

Yong Lu; Yu Yang; Fawei Zheng; Bao-Tian Wang; Ping Zhang

paper

Electronic, mechanical, and thermodynamic properties of americium dioxide

arXiv:1211.0378

Abstract

By performing density functional theory (DFT) + $U$ calculations, we systematically study the electronic, mechanical, tensile, and thermodynamic properties of AmO $_{2}$ . The experimentally observed antiferromagnetic insulating feature [J. Chem. Phys. 63, 3174 (1975)] is successfully reproduced. It is found that the chemical bonding character in AmO $_{2}$ is similar to that in PuO $_{2}$ , with smaller charge transfer and stronger covalent interactions between americium and oxygen atoms. The valence band maximum and conduction band minimum are contributed by 2 $p - 5 f$ hybridized and 5 $f$ electronic states respectively. The elastic constants and various moduli are calculated, which show that AmO $_{2}$ is less stable against shear forces than PuO $_{2}$ . The stress-strain relationship of AmO $_{2}$ is examined along the three low-index directions by employing the first-principles computational tensile test method. It is found that similar to PuO $_{2}$ , the [100] and [111] directions are the strongest and weakest tensile directions, respectively, but the theoretical tensile strengths of AmO $_{2}$ are smaller than those of PuO $_{2}$ . The phonon dispersion curves of AmO $_{2}$ are calculated and the heat capacities as well as lattice expansion curve are subsequently determined. The lattice thermal conductance of AmO $_{2}$ is further evaluated and compared with attainable experiments. Our present work integrally reveals various physical properties of AmO $_{2}$ and can be referenced for technological applications of AmO $_{2}$ based materials.

23 pages, 8 figures