The Ordered Structure of TiO<sub>1.25</sub>

Watanabe, Dai; Terasaki, Osamu; Jostsons, A.; Castles, J. R.

doi:10.1143/jpsj.25.292

Cited by 38 publications

(12 citation statements)

References 4 publications

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“…Disordered phase is in thermodynamic equilibrium at temperatures higher than 1263 K [2]. Annealing at a temperature below 1263 K results in a redistribution of structural vacancies within the basic B1 structure and formation of ordered phases [2,4,6,7]. Monoclinic phase Ti 5 O 5 (Ti 5 ■ 1 O 5 □ 1 ) appears as a result of ordering when y¼1.0 [2,4,6].…”

Section: Introductionmentioning

confidence: 99%

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

Kostenko

Lukoyanov

Zhukov

et al. 2013

Journal of Solid State Chemistry

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a b s t r a c tThe electronic structure and stability of three phases of titanium monoxide TiO y with B1 type of the basic structure have been studied. Cubic phase without structural vacancies, TiO, and two phases with structural vacancies, monoclinic Ti 5 O 5 and cubic disordered TiO 1.0 , was treated by means of firstprinciples calculations within the density functional theory with pseudo-potential approach based on the plane wave's basis. The ordered monoclinic phase Ti 5 O 5 was found to be the most stable and the cubic TiO without vacancies the less stable one. The role of structural vacancies in the titanium sublattice is to decrease the Fermi energy, the role of vacancies in the oxygen sublattice is to contribute to the appearance of Ti-Ti bonding interactions through these vacancies and to reinforce the Ti-Ti interactions close to them. Listed effects are significantly pronounced if the vacancies in the titanium and oxygen sublattices are associated in the so called "vacancy channels" which determine the formation of vacancy ordered structure of monoclinic Ti 5 O 5 -type.

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Section: Introductionmentioning

confidence: 99%

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

Kostenko

Lukoyanov

Zhukov

et al. 2013

Journal of Solid State Chemistry

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“…Upon slow anneal ing below 1263 K, vacancies are redistributed over the sites of the sublattices of the basis structure. As a result of such a redistribution, various ordered phases are formed [21][22][23][24]. If y = 1.0, the Ti 5 O 5 monoclinic superstructure is formed as a result of ordering.…”

Section: Calculation Of Internal Energymentioning

confidence: 99%

“…Upon an increase of the long range order parameter, the internal energy of the com pound decreases. This means that at low tempera tures, when the contribution of the entropy to the free energy is small, the ordered state of the system is ener getically more advantageous as compared to the disor dered state, which corresponds to experimental data [21][22][23][24].…”

Section: Calculation Of Internal Energymentioning

confidence: 99%

Internal energy and parameters of the order-disorder phase transition in titanium monoxide TiO y

Kostenko

Rempel

Lukoyanov

2013

J. Exp. Theor. Phys.

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Abstract-Quantum mechanical ab initio calculations are used to simulate the free energy functions for tita nium monoxide TiO y . The effect of the long range order of the Ti 5 O 5 type superstructure on the internal energy of the compound is studied by the supercell method. The dependences of the configuration entropy and free energy on the long range order parameter are determined. It is found that the order-disorder phase transition in titanium monoxide must occur in accordance with the mechanism of the first order phase tran sition with a critical value of the long range order parameter of 0.971. The calculated parameters of the phase transition are compared with the experimental data and the results obtained using the model of point charges and by calculating the Madelung energy. It is concluded that the short range order and the phonon entropy must be taken into account in calculating the equilibrium phase diagrams for strongly nonstoichiometric compounds.

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“…During a slow annealing below 1263 K, there occurs a redistribution of vacancies over sites of the sublattices of the basic structure, which results in the formation of ordered phases [2,3,5,6]. For titanium monoxide with the stoichiometric composition (y = 1.0), the ordering leads to the formation of the ordered mono clinic phase Ti 5 Theoretical investigations of the electronic struc ture, as well as calculations of the total energy and the enthalpy of formation of titanium monoxide, which are presented in [7][8][9][10][11][12], have demonstrated that the ordered structure Ti 5 1 O 5 ᮀ 1 is energetically more favorable as compared to the disordered structure.…”

Section: Introductionmentioning

confidence: 99%

“…At the same time, the disordered cubic phase TiO y has a very wide homogeneity region with the lower boundary lying in the range of 0.7-0.9 and the upper boundary in the range of 1.25-1.33 [2][3][4][5][6]15]. The homogeneity region of the ordered monoclinic phase Ti 5 O 5 (Ti 5 1 O 5 ᮀ 1 ), according to the data reported by Watanabe et al [2], lies in the range from 0.9 to 1.1, but according to the data presented by Mur ray and Wriedt [15], it is completely absent.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and stability of nonstoichiometric titanium monoxide TiO y with structural vacancies in one of the sublattices

2013

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Abstract-The electronic structure of nonstoichiometric titanium monoxide TiO y with different composi tions y, which contains structural vacancies either in the metallic sublattice or in the nonmetallic sublattice, has been investigated using the supercell method within the DFT GGA approximation with pseudopoten tials. The cases of ordered and disordered arrangements of vacancies have been considered. It has been found that the complete removal of vacancies from the sublattice is energetically unfavorable, and the ordering of oxygen vacancies according to the type of the Ti 6 O 5 ᮀ 1 superstructure, as well as titanium vacancies according to the Ti 5 1 O 6 type, does not lead to the stabilization of the B1 basic structure of titanium monoxide.

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The Ordered Structure of TiO_1.25

Cited by 38 publications

References 4 publications

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

Internal energy and parameters of the order-disorder phase transition in titanium monoxide TiO y

Electronic structure and stability of nonstoichiometric titanium monoxide TiO y with structural vacancies in one of the sublattices

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The Ordered Structure of TiO1.25

Cited by 38 publications

References 4 publications

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

Internal energy and parameters of the order-disorder phase transition in titanium monoxide TiO y

Electronic structure and stability of nonstoichiometric titanium monoxide TiO y with structural vacancies in one of the sublattices

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The Ordered Structure of TiO_1.25