研究目的
To investigate the structure and the ferroelectricity of the single crystal PMN(0.75)-PT(0.25) using first-principles density functional studies.
研究成果
The study concludes that [111]-direction ordering monoclinic and triclinic structures are more stable than [001]- and [011]-ordering tetragonal and monoclinic ones in PMN(0.75)-PT(0.25). Some ordered structures exhibit strong piezoelectric characteristics, providing useful information for multiscale modeling of relaxor-ferroelectrics.
研究不足
The study is limited to the investigation of ordered structures of PMN(0.75)-PT(0.25) and does not explore the effects of disorder or other compositions. The computational methods used may have limitations in accurately predicting all physical properties due to the approximations involved in DFT and LDA.
1：Experimental Design and Method Selection:
The study employs first-principles density functional theory (DFT) calculations using the Vienna ab initio simulation package (VASP) with local density approximation (LDA) framework and augmented projected augmented wave (PAW) pseudopotentials.
2：Sample Selection and Data Sources:
Ordered supercells with PMN(
3：75)-PT(25) stoichiometry are considered, specifically 1x1x4 and 2x1x2 supercell structures. List of Experimental Equipment and Materials:
The study uses the VASP code for calculations.
4：Experimental Procedures and Operational Workflow:
All atoms were relaxed using the conjugate gradient method until residual forces on constituent atoms became smaller than 5x10^-2 eV/?. The Brillouin zone integration was performed using Monkhorst-Pack k-point mesh.
5：Data Analysis Methods:
The linear response computations used the density functional perturbation theory (DFPT) to compute the electronic dielectric tensors and piezoelectric tensors.
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