Perovskite ferroelectrics play an essential role in modern science and technology.The excellent properties of perovskites are closely related to their lattice dynamics.Potassium tantalate niobate(KTa_(1-x)Nb_(x)O_(3),...Perovskite ferroelectrics play an essential role in modern science and technology.The excellent properties of perovskites are closely related to their lattice dynamics.Potassium tantalate niobate(KTa_(1-x)Nb_(x)O_(3),abbreviated as KTN)is a typical solid-solution perovskite with superior properties.Although the optical and electrical performances of KTN crystals have been widely explored,information on their lattice dynamics is still scarce,which partially limits the research and performance optimization of KTN.As a solid-solution,spontaneous polarization of KTN exhibits strong tunability,and there is stress within KTN.Here,we performed first-principles calculations in conjunction with experiments to investigate the polarization-and stress-related lattice dynamics in KTN.We assigned the vibration modes of observed Raman peaks,and established the relationship between spontaneous polarization and vibration.Especially,the lattice dynamics evolution of KTN crystal under stress was investigated.And the results provide insights into the regulatory effect of stress on dielectric property from the perspective of lattice dynamics.Finally,the variation trends of phonons under stress,as well as the mechanism of stress effect in tetragonal perovskites were explained.The conclusions drawn for KTN crystal were generalized to tetragonal ferroelectric systems.Our results help to reflect spontaneous polarization and structural characteristics distribution through non-destructive Raman spectra,and give a reference for improving performance by regulating lattice dynamics.The findings will hopefully guide research on performance origin and refined design of perovskite functional materials.展开更多
Studying the causes of summer(June–July–August)precipitation anomalies in the middle and lower reaches of the Yangtze River(MLYR)and accurately predicting rainy season precipitation are important to society and the ...Studying the causes of summer(June–July–August)precipitation anomalies in the middle and lower reaches of the Yangtze River(MLYR)and accurately predicting rainy season precipitation are important to society and the economy.In recent years,the sea surface temperature(SST)trend factor has been used to construct regression models for summer precipitation.In this study,through correlation analysis,winter SST anomaly predictors and the winter Central Pacific SST trend predictor(CPT)are identified as closely related to the following MLYR summer precipitation(YRSP).CPT can influence YRSP by inducing anomalous circulations over the North Pacific,guiding warm and moist air northward,and inhibiting the development of the anomalous anticyclone over the Northwest Pacific.This has improved the predictive skill of the seasonal regression model for YRSP.After incorporating the CPT,the correlation coefficient of the YRSP regression model improved by 40%,increasing from 0.45 to 0.63,and the root mean squared error decreased by 22%,from 1.15 to 0.90.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.12004085 and 12074092)the Fundamental Research Funds for the Central Universities(No.2023FRFK06004)+2 种基金the Natural Science Foundation of Heilongjiang Province of China(Nos.YQ2022A010 and ZD2022E003)the fellow-ship of China National Postdoctoral Program for Innovative Talents(No.BX20200111)the Heilongjiang Postdoctoral Funds(Nos.LBH-Z20065 and LBH-Z22121).
文摘Perovskite ferroelectrics play an essential role in modern science and technology.The excellent properties of perovskites are closely related to their lattice dynamics.Potassium tantalate niobate(KTa_(1-x)Nb_(x)O_(3),abbreviated as KTN)is a typical solid-solution perovskite with superior properties.Although the optical and electrical performances of KTN crystals have been widely explored,information on their lattice dynamics is still scarce,which partially limits the research and performance optimization of KTN.As a solid-solution,spontaneous polarization of KTN exhibits strong tunability,and there is stress within KTN.Here,we performed first-principles calculations in conjunction with experiments to investigate the polarization-and stress-related lattice dynamics in KTN.We assigned the vibration modes of observed Raman peaks,and established the relationship between spontaneous polarization and vibration.Especially,the lattice dynamics evolution of KTN crystal under stress was investigated.And the results provide insights into the regulatory effect of stress on dielectric property from the perspective of lattice dynamics.Finally,the variation trends of phonons under stress,as well as the mechanism of stress effect in tetragonal perovskites were explained.The conclusions drawn for KTN crystal were generalized to tetragonal ferroelectric systems.Our results help to reflect spontaneous polarization and structural characteristics distribution through non-destructive Raman spectra,and give a reference for improving performance by regulating lattice dynamics.The findings will hopefully guide research on performance origin and refined design of perovskite functional materials.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(42175061)。
文摘Studying the causes of summer(June–July–August)precipitation anomalies in the middle and lower reaches of the Yangtze River(MLYR)and accurately predicting rainy season precipitation are important to society and the economy.In recent years,the sea surface temperature(SST)trend factor has been used to construct regression models for summer precipitation.In this study,through correlation analysis,winter SST anomaly predictors and the winter Central Pacific SST trend predictor(CPT)are identified as closely related to the following MLYR summer precipitation(YRSP).CPT can influence YRSP by inducing anomalous circulations over the North Pacific,guiding warm and moist air northward,and inhibiting the development of the anomalous anticyclone over the Northwest Pacific.This has improved the predictive skill of the seasonal regression model for YRSP.After incorporating the CPT,the correlation coefficient of the YRSP regression model improved by 40%,increasing from 0.45 to 0.63,and the root mean squared error decreased by 22%,from 1.15 to 0.90.
