A comprehensive DFT investigation of bulk and low-index surfaces of ZrO₂polymorphs

Abstract

The bulk structure, the relative stability, and the electronic properties of monoclinic, tetragonal, and cubic ZrO(2) have been studied from a theoretical point of view, through periodic ab initio calculations using different Gaussian basis sets together with Hartree-Fock (HF), pure Density Functional Theory (DFT), and mixed HF/DFT schemes as found in hybrid functionals. The role of a posteriori empirical correction for dispersion, according to the Grimme D2 scheme, has also been investigated. The obtained results show that, among the tested functionals, PBE0 not only provides the best structural description of the three polymorphs, but it also represents the best compromise to accurately describe both the geometric and electronic features of the oxide. The relative stability of the three phases can also be qualitatively reproduced, as long as thermal contributions to the energy are taken into account. Four low-index ZrO(2) surfaces [monoclinic (-111), tetragonal (101 and 111), and cubic (111)] have then been studied at this latter level of theory. Surface energies, atomic relaxations, and electronic properties of these surfaces have been computed. The most stable surface is the cubic one, which is associated to small relaxations confined to the outermost layers. It is followed by the monoclinic (-111) and the tetragonal (101), which have very similar surface energies and atomic displacements. The tetragonal (111) was instead found to be, by far, the less stable with large displacements not only for the outermost but also for deeper layers. Through the comparison of different methods and basis sets, this study allowed us to find a reliable and accurate computational protocol for the investigation of zirconia, both in its bulk and surfaces forms, in view of more complex technological applications, such as ZrO(2) doped with aliovalent oxides as found in solid oxide fuel cells.

Energy Landscape of Zirconia Phase Transitions

“…Our theoretical calculations confirm that the t phase becomes more stable than the m phase above 1580 K, which is consistent with previous calculations (1560 K) 22 and the experiment observation (1480− 1550 K). 23,24 (Transition temperature is reduced to 1450 K when hybrid HSE06 functional is utilized instead; Supporting Information)…”

Hybrid Fuel Cells with Carbonate/Oxide Composite Electrolytes: An Electrochemical and Theoretical Insight

“…Finally, for the Y atoms, the Hay and Wadt (16)(17)(18) small core ECP and the 31G(d) basis set (22) for the (4s 2 4p 6 5s 2 4d 1 ) valence electrons have been used. These basis sets showed to perform closely to larger ones (15).…”

“…The global hybrid functional PBE0 13,14 , a parameter-free functional mixing 25% of HF exchange in a PBE scheme, has been selected as the exchange-correlation functional of choice (15).…”

Estudos <i>ab initio</i> das propriedades estruturais, energéticas e eletrônicas de clusters de óxidos mistos de Ce_15-nZr_nO₃₀,(n=0-15)

“…Além disso, o óxido de zircônio possui várias formas alotrópicas como a monoclínica, tetragonal, cúbica, fluorita entre outras, que dependem das condições de temperatura e pressão. 31,32 Dessa forma, o Zr tem um elevado potencial de aplicação em diversas áreas tecnológicas, sendo aplicado em catalisadores, células solares e combustíveis, fotocatálise, biomedicina, sensor de gás automotivos, como em implantes de quadril e em restaurações e implantação dentárias, como barreira térmica em revestimentos, em engenharia cerâmica como um endurecimento de cerâmica e agente fortalecedor devido a sua alta tenacidade e dureza, entre outros. [32][33][34][35] Em virtude do grande número de aplicações de ambos os óxidos de Ce e Zr, há um grande interesse no desenvolvimento e estudo de novos materiais a partir destes óxidos.…”

“…6 uma compactação dos clusters de menor energia, pois seu raio é a metade do valor do de maior energia relativa. literatura, 25,32,81,82 as quais são designadas como estruturas mais estáveis na fase cristalina, destes óxidos. Também foram realizados cálculos, para confirmar esta estabilidade e bem como para outras estruturas simétricas, como por exemplo, estrutura anatase que é uma das três formas da estruturas cristalinas do dióxido de titânio.…”