Atomic and Electronic Structures and Glass Formation of La 4 Ti 9 O 24 Glass From First‐Principles Molecular Dynamics

ABSTRACT High‐refractive index La 4 Ti 9 O 24 glass exhibits several unconventional structural features compared with typical network‐former oxide glasses, including a high oxygen packing density, Ti–O coordination numbers close to 6, and a substantial fraction of edge‐sharing TiO n polyhedra. Herein, first‐principles molecular dynamics simulations were conducted to refine classical molecular dynamics models. The constructed models yielded an average Ti–O coordination number of 5.8 and an edge‐sharing fraction of approximately 30%. The electronic density of states, dielectric functions, and refractive index dispersion for La 4 Ti 9 O 24 glass were also calculated to quantitatively elucidate the optical properties. A two‐dimensional projection of the structural model using the reduced atomic arrangement method further revealed that in this glass, oxide ions adopt a nearly close‐packed configuration, while La 3+ ions also occupy nearly close‐packed sites but exclusively at positions not occupied by O 2− , and Ti 4+ ions fill a part of the interstitial sites within the oxygen framework. These results suggest that the unconventional glass formation of the La 2 O 3 –TiO 2 binary system is closely related to the stabilization of a disordered network through edge‐sharing connectivity within nearly close‐packed framework.