Effect of the Local Atomic Ordering on the Stability of β‑Spodumene

This study focuses on the relative
energetic stability of β-spodumene configurations with different
atomic ordering, evaluated using electronic structure methods based
on static periodic density functional theory. We found that β-spodumene
configurations with a framework containing exclusively Al–O–Si
linkages are energetically the most stable, consistent with the aluminum
avoidance principle. A correlation between the interstitial sites
occupied by lithium and the stability of the configuration was established:
highly stable configurations contain greater proportions of lithium
associated with the edges of AlO4 tetrahedrons. The identified
low-energy configurations have a band gap of ∼4.8 eV, and similar
electronic band structures and densities of states. Both the PBE and
PBEsol functionals predict small differences in the relative stabilities
of the different configurations of β-spodumene. However, only
PBEsol is able to reproduce the experimentally observed stability
differences between α-spodumene and β-spodumene. β-Spodumene
is the preferred polymorph at high temperatures, with the PBEsol inversion
temperature from α- to β-spodumene predicted to occur
at 1070 K.