Ab initiostudy of neutral (TiO₂)_nclusters and their interactions with water and transition metal atoms

Abstract

We have systematically investigated the growth behavior and stability of small stoichiometric (TiO(2))(n) (n = 1-10) clusters as well as their structural, electronic and magnetic properties by using the first-principles plane wave pseudopotential method within density functional theory. In order to find out the ground state geometries, a large number of initial cluster structures for each n has been searched via total energy calculations. Generally, the ground state structures for the case of n = 1-9 clusters have at least one monovalent O atom, which only binds to a single Ti atom. However, the most stable structure of the n = 10 cluster does not have any monovalent O atom. On the other hand, Ti atoms are at least fourfold coordinated for the ground state structures for n ≥ 4 clusters. Our calculations have revealed that clusters prefer to form three-dimensional structures. Furthermore, all these stoichiometric clusters have nonmagnetic ground state. The formation energy and the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap for the most stable structure of (TiO(2))(n) clusters for each n have also been calculated. The formation energy and hence the stability increases as the cluster size grows. In addition, the interactions between the ground state structure of the (TiO(2))(n) cluster and a single water molecule have been studied. The binding energy (E(b)) of the H(2)O molecule exhibits an oscillatory behavior with the size of the clusters. A single water molecule preferably binds to the cluster Ti atom through its oxygen atom, resulting an average binding energy of 1.1 eV. We have also reported the interaction of the selected clusters (n = 3, 4, 10) with multiple water molecules. We have found that additional water molecules lead to a decrease in the binding energy of these molecules to the (TiO(2))(n) clusters. Finally, the adsorption of transition metal (TM) atoms (V, Co and Pt) on the n = 10 cluster has been investigated for possible functionalization. All these elements interact strongly with this cluster, and a permanent magnetic moment is induced upon adsorption of Co and V atoms. We have observed gap localized TM states leading to significant HOMO-LUMO gap narrowing, which is essential to achieve visible light response for the efficient use of TiO(2) based materials. In this way, electronic and optical as well as magnetic properties of TiO(2) materials can be modulated by using the appropriate adsorbate atoms.

Structural and Electronic Properties of Na2Ti3O7 and H2Ti3O7

“…In photocatalytic applications, the standard material of choice is titania (titanium dioxide, TiO 2 ), for its wide availability, low toxicity, high stability, and activity . Among TiO 2 polymorphs, anatase achieves the highest efficiency for photocatalytic applications, but the reasons for this are not clear.…”

Dissociative Water Adsorption on Gas-Phase Titanium Dioxide Cluster Anions Probed with Infrared Photodissociation Spectroscopy

“…Several theoretical groups have reported calculations of molecular and dissociative water adsorption and water splitting on small (TiO 2 ) n clusters [50][51][52][53][54][55][56]; others have studied these interactions on larger TiO 2 nanostructures [57][58][59][60]. The most thorough body of work comes from calculations by Dixon and coworkers [61][62][63] regarding water adsorption, hydrolysis, and H 2 /O 2 evolution on small neutral titanium dioxide clusters.…”

Electronic structures and optical spectra of thin anataseTiO2nanowires through hybrid density functional and quasiparticle calculations

“…Nanometer-sized materials come into view with preferable and interesting physical and chemical properties [21][22][23]. For instance, quasi-one-dimensional periodic structures facilitate the transport of the charge carriers.…”