研究目的
Investigating the accommodation and migration of oxygen vacancies in bulk hexagonal YMnO3 and studying interactions between neutral ferroelectric domain walls and oxygen vacancies.
研究成果
Oxygen vacancies in hexagonal YMnO3 are more stable in the Mn-O layers than at apical sites, with a preference for vacancies at the planar O4 sites in bulk. These vacancies are not likely to accumulate at neutral domain walls due to unfavorable Y-O bond lengths caused by the local strain field. The findings suggest that oxygen vacancies are not the origin of observed enhanced conductivity at neutral domain walls in hexagonal manganites.
研究不足
The study is limited by the computational methods used, which may not fully capture all aspects of the material's behavior under experimental conditions. Additionally, the focus on neutral domain walls may not account for the behavior of oxygen vacancies at charged domain walls.
1：Experimental Design and Method Selection:
Density functional theory (DFT) calculations were performed using the VASP code with the generalized-gradient-approximation Perdew-Burke-Ernzerhof (GGA PBEsol) functional for solids. A Hubbard U of 5 eV was added within the spin-polarized GGA+U implementation to better describe the Mn-d on-site Coulomb interaction.
2：Sample Selection and Data Sources:
The study focused on the bulk hexagonal YMnO3 structure and neutral ferroelectric domain walls within this material.
3：List of Experimental Equipment and Materials:
The VASP code was used for DFT calculations, with a plane-wave cutoff energy of 550 eV and a (cid:3)-centered 2 × 2 × 2 mesh for Brillouin zone integration.
4：Experimental Procedures and Operational Workflow:
The geometry of the bulk structures was relaxed until the forces on the ions were below
5：01 eV/? for 2 × 2 × 1 cells and 02 for 3 × 3 × 2 cells. Oxygen vacancy formation energies were calculated, and the ferroelectric polarization was calculated with a simple ionic point charge model. Data Analysis Methods:
The electronic density of states for each of the four vacant oxygen sites was analyzed, and the structural screening length was defined to quantify the distortions caused by oxygen vacancies.
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