Sehyeok Park - Academia.edu (original) (raw)

Papers by Sehyeok Park

Research paper thumbnail of Development of potential model for radiation damage simulation in α-Fe

Ferritic steels are widely used as components and structural materials in nuclear fission and fus... more Ferritic steels are widely used as components and structural materials in nuclear fission and fusion reactors [1][2]. Therefore, radiation damage processes and effects in ferritic steels has been the subject of extensive studies in decades. Classical molecular dynamics (CMD) simulations are widely used in this field, because it can treat a large simulation system and long simulation length required to pursue atomic motion during radiation damage processes. In general, the results of CMD simulation are dependent on the potential model used in the simulation. For radiation damage studies, threshold displacement energy (TDE), average number of Frenkel pair (FP) defect and atom displacement cross sections largely depend on the potential model [3]. In radiation damage simulations, it is common practice to join the potential model constructed with equilibrium state properties to the ZBL potential model, which is designed for atomic collision processes, using an arbitrary function. This ar...

Research paper thumbnail of Evaluation of Threshold Displacement Energy of Tungsten by Molecular Dynamics Simulation

Threshold displacement energy (TDE) is an important quantity to determine the number of defects f... more Threshold displacement energy (TDE) is an important quantity to determine the number of defects formed by irradiation of high-energy particles. For tungsten, different values of TDE have been reported in several studies, which caused discrepancy in calculated damage amounts. In the present study, we evaluated TDE using molecular dynamics simulation, where TDE is defined as the average value of minimum displacement energies to create a stable defect over all directions. In order to determine it accurately, effects of some calculation settings such as simulation cell size, the number of displacement directions and recoil energy increment value for average TDE calculating were analyzed. As a result, we obtained 83 eV as TDE of tungsten. This value is close to the one recommended value by American Society for Testing and Materials (ASTM) which is 90 eV.

Research paper thumbnail of Evaluation of the threshold displacement energy in tungsten by molecular dynamics calculations

Journal of Nuclear Materials, 2017

The threshold displacement energy of tungsten was determined by molecular dynamics calculations t... more The threshold displacement energy of tungsten was determined by molecular dynamics calculations to be 85 eV, which reasonably agree with the ASTM recommendation, 90 eV. A possible error was estimated to be 4.5% by systematic investigations on the effects of calculation settings such as the system size and the number of sampled recoil directions. We explained the reasons why large discrepancies in the threshold displacement energy were observed in previous studies.

Research paper thumbnail of Characterization and quantification of numerical errors in threshold displacement energy calculated by molecular dynamics in bcc-Fe

Computational Materials Science, 2019

The accumulation of radiation defects in nuclear fusion/fission materials often causes adverse ch... more The accumulation of radiation defects in nuclear fusion/fission materials often causes adverse changes in material properties. The threshold displacement energy (TDE) is one of the fundamental quantities used to evaluate the number of formed radiation defects. In the present study, to understand the error sources in TDE calculation using the molecular dynamics method and to find an optimal strategy for accurate and precise calculation, we analyze how the calculated TDE is affected by the calculation settings, including the system shape and size, the recoil energy increment in searching the threshold value, the sampling numbers of recoil directions and recoil event time samples, and the potential model. Bcc-Fe is used as a test material, and three potential models are employed for comparison. As a result, the calculation errors caused by these settings are successfully classified into accuracy error and precision error and then quantified. The type and trend of the error caused by each setting are not qualitatively different between the tested potential models, although they are quantitatively different. This potential model dependence can often be reasonably explained from the recoil direction dependence of the TDE and the defect formation mechanisms. Finally, using the equations derived to quantify the accuracy and precision of the calculated TDE and the calculation cost, we suggest some strategies to minimize the error with a given limited computational resource.

Research paper thumbnail of Development of potential model for radiation damage simulation in α-Fe

Ferritic steels are widely used as components and structural materials in nuclear fission and fus... more Ferritic steels are widely used as components and structural materials in nuclear fission and fusion reactors [1][2]. Therefore, radiation damage processes and effects in ferritic steels has been the subject of extensive studies in decades. Classical molecular dynamics (CMD) simulations are widely used in this field, because it can treat a large simulation system and long simulation length required to pursue atomic motion during radiation damage processes. In general, the results of CMD simulation are dependent on the potential model used in the simulation. For radiation damage studies, threshold displacement energy (TDE), average number of Frenkel pair (FP) defect and atom displacement cross sections largely depend on the potential model [3]. In radiation damage simulations, it is common practice to join the potential model constructed with equilibrium state properties to the ZBL potential model, which is designed for atomic collision processes, using an arbitrary function. This ar...

Research paper thumbnail of Evaluation of Threshold Displacement Energy of Tungsten by Molecular Dynamics Simulation

Threshold displacement energy (TDE) is an important quantity to determine the number of defects f... more Threshold displacement energy (TDE) is an important quantity to determine the number of defects formed by irradiation of high-energy particles. For tungsten, different values of TDE have been reported in several studies, which caused discrepancy in calculated damage amounts. In the present study, we evaluated TDE using molecular dynamics simulation, where TDE is defined as the average value of minimum displacement energies to create a stable defect over all directions. In order to determine it accurately, effects of some calculation settings such as simulation cell size, the number of displacement directions and recoil energy increment value for average TDE calculating were analyzed. As a result, we obtained 83 eV as TDE of tungsten. This value is close to the one recommended value by American Society for Testing and Materials (ASTM) which is 90 eV.

Research paper thumbnail of Evaluation of the threshold displacement energy in tungsten by molecular dynamics calculations

Journal of Nuclear Materials, 2017

The threshold displacement energy of tungsten was determined by molecular dynamics calculations t... more The threshold displacement energy of tungsten was determined by molecular dynamics calculations to be 85 eV, which reasonably agree with the ASTM recommendation, 90 eV. A possible error was estimated to be 4.5% by systematic investigations on the effects of calculation settings such as the system size and the number of sampled recoil directions. We explained the reasons why large discrepancies in the threshold displacement energy were observed in previous studies.

Research paper thumbnail of Characterization and quantification of numerical errors in threshold displacement energy calculated by molecular dynamics in bcc-Fe

Computational Materials Science, 2019

The accumulation of radiation defects in nuclear fusion/fission materials often causes adverse ch... more The accumulation of radiation defects in nuclear fusion/fission materials often causes adverse changes in material properties. The threshold displacement energy (TDE) is one of the fundamental quantities used to evaluate the number of formed radiation defects. In the present study, to understand the error sources in TDE calculation using the molecular dynamics method and to find an optimal strategy for accurate and precise calculation, we analyze how the calculated TDE is affected by the calculation settings, including the system shape and size, the recoil energy increment in searching the threshold value, the sampling numbers of recoil directions and recoil event time samples, and the potential model. Bcc-Fe is used as a test material, and three potential models are employed for comparison. As a result, the calculation errors caused by these settings are successfully classified into accuracy error and precision error and then quantified. The type and trend of the error caused by each setting are not qualitatively different between the tested potential models, although they are quantitatively different. This potential model dependence can often be reasonably explained from the recoil direction dependence of the TDE and the defect formation mechanisms. Finally, using the equations derived to quantify the accuracy and precision of the calculated TDE and the calculation cost, we suggest some strategies to minimize the error with a given limited computational resource.