We propose an active learning scheme for automatically sampling a minimum number of uncorrelated configurations for fitting the Gaussian Approximation Potential(GAP).Our active learning scheme consists of an unsupervi...We propose an active learning scheme for automatically sampling a minimum number of uncorrelated configurations for fitting the Gaussian Approximation Potential(GAP).Our active learning scheme consists of an unsupervised machine learning(ML)scheme coupled with a Bayesian optimization technique that evaluates the GAP model.We apply this scheme to a Hafnium dioxide(HfO2)dataset generated from a“melt-quench”ab initio molecular dynamics(AIMD)protocol.Our results show that the active learning scheme,with no prior knowledge of the dataset,is able to extract a configuration that reaches the required energy fit tolerance.Further,molecular dynamics(MD)simulations performed using this active learned GAP model on 6144 atom systems of amorphous and liquid state elucidate the structural properties of HfO2 with near ab initio precision and quench rates(i.e.,1.0 K/ps)not accessible via AIMD.The melt and amorphous X-ray structural factors generated from our simulation are in good agreement with experiment.In addition,the calculated diffusion constants are in good agreement with previous ab initio studies.展开更多
Complex microstructure changes occur in nuclear fuel and structural materials due to the extreme environments of intense irradiation and high temperature.This paper evaluates the role of the phase field method in pred...Complex microstructure changes occur in nuclear fuel and structural materials due to the extreme environments of intense irradiation and high temperature.This paper evaluates the role of the phase field method in predicting the microstructure evolution of irradiated nuclear materials and the impact on their mechanical,thermal,and magnetic properties.The paper starts with an overview of the important physical mechanisms of defect evolution and the significant gaps in simulating microstructure evolution in irradiated nuclear materials.Then,the phase field method is introduced as a powerful and predictive tool and its applications to microstructure and property evolution in irradiated nuclear materials are reviewed.The review shows that(1)Phase field models can correctly describe important phenomena such as spatial-dependent generation,migration,and recombination of defects,radiation-induced dissolution,the Soret effect,strong interfacial energy anisotropy,and elastic interaction;(2)The phase field method can qualitatively and quantitatively simulate two-dimensional and three-dimensional microstructure evolution,including radiation-induced segregation,second phase nucleation,void migration,void and gas bubble superlattice formation,interstitial loop evolution,hydrate formation,and grain growth,and(3)The Phase field method correctly predicts the relationships between microstructures and properties.The final section is dedicated to a discussion of the strengths and limitations of the phase field method,as applied to irradiation effects in nuclear materials.展开更多
基金This material is based upon work supported by Laboratory Directed Research and Development funding from Argonne National Laboratory,provided by the Director,Office of Science,of the U.S.Department of Energy(DOE)under Contract No.DEAC02-06CH11357This research used resources of the Argonne Leadership Computing Facility,which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357+3 种基金Argonne National Laboratory’s work was supported by the U.S.DOE,Office of Science,under contract DE-AC02-06CH11357This research used resources of the Advanced Photon Source,a U.S.DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357Use of the Center for Nanoscale Materials,an Office of Science user facility,was supported by the U.S.DOE,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357C.H.and A.N.K gratefully acknowledges useful discussions with Dr.Jens Smiatek,Dr.Frank Uhlig,and financial support from the German Funding Agency(Deutsche Forschungsgemeinschaft-DFG)under Germany’s Excellence Strategy—EXC 2075—390740016.
文摘We propose an active learning scheme for automatically sampling a minimum number of uncorrelated configurations for fitting the Gaussian Approximation Potential(GAP).Our active learning scheme consists of an unsupervised machine learning(ML)scheme coupled with a Bayesian optimization technique that evaluates the GAP model.We apply this scheme to a Hafnium dioxide(HfO2)dataset generated from a“melt-quench”ab initio molecular dynamics(AIMD)protocol.Our results show that the active learning scheme,with no prior knowledge of the dataset,is able to extract a configuration that reaches the required energy fit tolerance.Further,molecular dynamics(MD)simulations performed using this active learned GAP model on 6144 atom systems of amorphous and liquid state elucidate the structural properties of HfO2 with near ab initio precision and quench rates(i.e.,1.0 K/ps)not accessible via AIMD.The melt and amorphous X-ray structural factors generated from our simulation are in good agreement with experiment.In addition,the calculated diffusion constants are in good agreement with previous ab initio studies.
基金supported by the US Department of Energy’s Nuclear Energy Advanced Modeling and Simulation(NEAMS)Program in Pacific Northwest National Laboratory(PNNL),which is operated by Battelle Memorial Institute for the US Department of Energy under Contract No.DE-AC05-76RL01830.
文摘Complex microstructure changes occur in nuclear fuel and structural materials due to the extreme environments of intense irradiation and high temperature.This paper evaluates the role of the phase field method in predicting the microstructure evolution of irradiated nuclear materials and the impact on their mechanical,thermal,and magnetic properties.The paper starts with an overview of the important physical mechanisms of defect evolution and the significant gaps in simulating microstructure evolution in irradiated nuclear materials.Then,the phase field method is introduced as a powerful and predictive tool and its applications to microstructure and property evolution in irradiated nuclear materials are reviewed.The review shows that(1)Phase field models can correctly describe important phenomena such as spatial-dependent generation,migration,and recombination of defects,radiation-induced dissolution,the Soret effect,strong interfacial energy anisotropy,and elastic interaction;(2)The phase field method can qualitatively and quantitatively simulate two-dimensional and three-dimensional microstructure evolution,including radiation-induced segregation,second phase nucleation,void migration,void and gas bubble superlattice formation,interstitial loop evolution,hydrate formation,and grain growth,and(3)The Phase field method correctly predicts the relationships between microstructures and properties.The final section is dedicated to a discussion of the strengths and limitations of the phase field method,as applied to irradiation effects in nuclear materials.
