DFT+U is a widely used treatment in the density functional theory(DFT)to deal with correlated materials that contain open-shell elements,whereby the quantitative and sometimes even qualitative failures of local and se...DFT+U is a widely used treatment in the density functional theory(DFT)to deal with correlated materials that contain open-shell elements,whereby the quantitative and sometimes even qualitative failures of local and semi-local approximations can be corrected without much computational overhead.However,finding appropriate U parameters for a given system and structure is non-trivial and computationally intensive,because the U value has generally a strong chemical and structural dependence.In this work,we address this issue by building a machine learning(ML)model that enables the prediction of material-and structure-specific U values at nearly no computational cost.Using Mn–O system as an example,the ML model is trained by calibrating DFT+U electronic structures with the hybrid functional results of more than 3000 structures.The model allows us to determine an accurate U value(MAE=0.128 eV,R^(2)=0.97)for any given Mn–O structure.Further analysis reveals that M–O bond lengths are key local structural properties in determining the U value.This approach of the ML U model is universally applicable,to significantly expand and solidify the use of the DFT+U method.展开更多
The potential risks of perfluorooctane sulfonate （PFOS） are of increasing ecological concern. Swimming performance is linked to the fitness and health of fish. However, the impacts of PFOS on swimming performance re...The potential risks of perfluorooctane sulfonate （PFOS） are of increasing ecological concern. Swimming performance is linked to the fitness and health of fish. However, the impacts of PFOS on swimming performance remain largely unknown. We investigated the ecotoxicological effects of acute exposure to PFOS on the swimming performance and energy expenditure of juvenile goldfish （Carassius auratus）. The fish were exposed to a range of PFOS concentrations （0, 0.5, 2, 8 and 32 mg/L） for 48 hr. The spontaneous swimming activity, fast-start swimming performance, critical swimming speed （Ucrit） and active metabolic rate （AMR） of the goldfish were examined after exposure to PFOS. PFOS exposure resulted in remarkable effects on spontaneous activity. Motion distance was reduced, and the proportion of motionless time increased with increasing concentrations of PFOS. However, no significant alterations in the fast-start performance-related kinematic parameters, such as latency time, maximum linear velocity, maximum linear acceleration or escape distance during the first 120 msec after stimulus, were observed after PFOS exposure. Unexpectedly, although PFOS exposure had marked influences on the swimming oxygen consumption rates and AMR of goldfish, the U crit of the goldfish was not significantly affected by PFOS. This may result in a noteworthy increase in the energetic cost of transport. The overall results indicate that, in contrast to spontaneous activity, underlying swimming capabilities are maintained in goldfish after short-term exposure to PFOS, but energy expenditure during the process of swimming is dramatically aggravated.展开更多
基金Chinese Academy of Sciences(Grant Nos.XDB33020000,CAS-WX2023SF-0101,ZDBS-LY-SLH007,and YSBR047)National Key R&D Program of China(2021YFA1400200,and 2021YFA0718700)National Natural Science Foundation of China(Grand Nos.12025407,12134012 and 12188101).
文摘DFT+U is a widely used treatment in the density functional theory(DFT)to deal with correlated materials that contain open-shell elements,whereby the quantitative and sometimes even qualitative failures of local and semi-local approximations can be corrected without much computational overhead.However,finding appropriate U parameters for a given system and structure is non-trivial and computationally intensive,because the U value has generally a strong chemical and structural dependence.In this work,we address this issue by building a machine learning(ML)model that enables the prediction of material-and structure-specific U values at nearly no computational cost.Using Mn–O system as an example,the ML model is trained by calibrating DFT+U electronic structures with the hybrid functional results of more than 3000 structures.The model allows us to determine an accurate U value(MAE=0.128 eV,R^(2)=0.97)for any given Mn–O structure.Further analysis reveals that M–O bond lengths are key local structural properties in determining the U value.This approach of the ML U model is universally applicable,to significantly expand and solidify the use of the DFT+U method.
基金supported by the Natural Science Foundation Project of Chongqing (No. CSTC2011jjA20006)the Research Project of Chongqing Education Committee (No. KJ110606)the projects of Chongqing Normal University (No. 2011XLZ11, 10XLB037)
文摘The potential risks of perfluorooctane sulfonate （PFOS） are of increasing ecological concern. Swimming performance is linked to the fitness and health of fish. However, the impacts of PFOS on swimming performance remain largely unknown. We investigated the ecotoxicological effects of acute exposure to PFOS on the swimming performance and energy expenditure of juvenile goldfish （Carassius auratus）. The fish were exposed to a range of PFOS concentrations （0, 0.5, 2, 8 and 32 mg/L） for 48 hr. The spontaneous swimming activity, fast-start swimming performance, critical swimming speed （Ucrit） and active metabolic rate （AMR） of the goldfish were examined after exposure to PFOS. PFOS exposure resulted in remarkable effects on spontaneous activity. Motion distance was reduced, and the proportion of motionless time increased with increasing concentrations of PFOS. However, no significant alterations in the fast-start performance-related kinematic parameters, such as latency time, maximum linear velocity, maximum linear acceleration or escape distance during the first 120 msec after stimulus, were observed after PFOS exposure. Unexpectedly, although PFOS exposure had marked influences on the swimming oxygen consumption rates and AMR of goldfish, the U crit of the goldfish was not significantly affected by PFOS. This may result in a noteworthy increase in the energetic cost of transport. The overall results indicate that, in contrast to spontaneous activity, underlying swimming capabilities are maintained in goldfish after short-term exposure to PFOS, but energy expenditure during the process of swimming is dramatically aggravated.
