Crystal Structures and Electronic Properties of Oxygen-rich Titanium Oxides at High Pressure

Abstract

Pressure is well-known to significantly change the bonding patterns of materials and lift the reactivity of elements, leading to the synthesis of unconventional compounds with fascinating properties. Titanium-oxygen (Ti-O) compounds (e.g., TiO) are attracting increasing attention due to their attractive electronic properties and extensive industrial applications (e.g., photocatalysis and solar cells). Using the effective CALYPSO structure searching method combined with first-principles calculations, we theoretically explored various oxygen-rich Ti-O compounds at pressures ranging from 0 to 200 GPa. Our results revealed, unexpectedly, that pressure stabilizes two hitherto unknown stoichiometric oxygen-rich TiO and TiO compounds. TiO crystallized in P-42 c structure, whose remarkable feature is that it contains a peroxide group (O2) with an O-O distance of 1.38 Å at 150 GPa. The trioxide TiO is an ionic metal and is the oxygen-richest compound known thus far in the Ti-O system. It adopts a high symmetry (space group Pm-3 n) structure consisting of a 12-fold coordinated face-sharing TiO icosahedron, where Ti has the highest coordination number with O among all Ti-O structures. The underlying mechanisms for the stabilization of TiO and TiO lie in the higher coordination number and denser structure packing. Our current results unravel the unusual oxygen-rich stoichiometry of Ti-O compounds and provide further insight into the diverse electronic properties of Ti oxides under high pressure.

Predicting the structure and stability of titanium oxide electrides

“…Structure patterns able to provide open interstitial regions play also an irreplaceable role in the stabilization of electrides. Though most of our newly predicted Ti-rich oxides are good electrides, the ambient pressure α-phase, high pressure NaCl-type, 45,46 and CsCl-type 34 phases of Ti-rich TiO compound are not candidates of electrides since the structures are rather compact without exhibiting any atom-sized cavity in the lattice. Even for our predicted Ti 5 O compound, once the electride structure at ambient pressure transforms into the high-pressure phase of C2/m structure (Fig.…”

“…The effectiveness of this method is benchmarked on various known systems. 14,18,[33][34][35][36][37][38][39][40][41][42] The electronic structures of the most stable structures were calculated using the same settings as the structure re-relaxation step, except denser Monkhorst-Pack grids with a spacing of around 2π × 0.01 Å −1 was used in the density of states (DOS) calculations.…”

Synthesis of BiSI/Ag2CO3 Composite Material for Photocatalytic Degradation of Rhodamine B under Visible Light**

“…[3][4] Although traditional photocatalysts such as TiO 2 have some advantages of good stability, nontoxicity, high activity and low cost, they also have some drawbacks, which limit their practical application ability. [5][6][7][8][9][10][11][12] Therefore, to degrade pollutants more effectively, it is particularly important to apply a novel visiblelight-driven photocatalyst with high activity and stability.…”

Synthesis of BiSI/Ag2CO3 Composite Material for Photocatalytic Degradation of Rhodamine B under Visible Light

“…In recent years, semiconductor photocatalysis technology has attracted great attention in the eld of environmental protection due to its obvious advantages of low economic cost, no secondary pollution to degrade the organic pollutants. Although traditional photocatalysts such as TiO 2 has some advantages of good stability, nontoxicity, high activity and low cost, it still has some drawbacks, which limit its practical application ability [1][2][3][4][5][6][7][8] . Therefore, in order to degrade pollutants more effectively, it is more important to apply a new type of visible light-driven photocatalyst with high activity and stability.…”