Anhui Fuhuang Architectural Design Research (China)

The functionality of ferroelectrics is often constrained by their Curie temperature, above which depolarization occurs. Lithium (Li) is the only experimentally known substitute that can increase the Curie temperature in ferroelectric niobate-based perovskites, yet the mechanism remains unresolved. Here, the unique phenomenon in Li-substituted KNbO3 is investigated using first-principles density functional theory. Theoretical calculations show that Li substitution at the A-site of perovskite introduces compressive chemical pressure, reducing Nb–O hybridization and associated ferroelectric instability. However, the large off-center displacement of the Li cation compensates for this reduction and further enhances the soft polar mode, thereby raising the Curie temperature. In addition, the stability of the tetragonal phase over the orthorhombic phase is predicted upon Li substitution, which reasonably explains the experimental observation of a decreased orthorhombic-to-tetragonal phase transition temperature. Finally, a metastable anti-phase polar state in which the Li cation displaces oppositely to the Nb cation is revealed, which could also contribute to the variation of phase transition temperatures. These findings provide critical insights into the atomic-scale mechanisms governing Curie temperature enhancement in ferroelectrics and pave the way for designing advanced ferroelectric materials with improved thermal stability and functional performance.

In order to improve the risk assessment effect of infrastructure projects, this paper combines the BP-ANN algorithm to conduct risk assessment and analysis of overseas infrastructure projects to avoid the problem of slow learning and speed up network learning. Moreover, this paper normalizes the input value, and redefines the concept of risk on the basis of previous research. In addition, this paper sets up to record the basic information and risk-related information of the project. In order to verify the effectiveness of the algorithm, this paper predicts the training data, test data, and verification data, respectively, to verify the effectiveness of the algorithm, and collects existing overseas infrastructure project cases as samples to perform the simulation experiments. The experimental study shows that the risk assessment model of overseas infrastructure projects that integrates the BP-ANN algorithm proposed in this paper has a good risk analysis effect.