Molecular dynamics study of interactions between edge dislocation and irradiation-induced defects in Fe–10Ni–20Cr alloy

Irradiation-induced defects frequently impede the slip of dislocations, resulting in a sharp decline in the performance of nuclear reactor structural materials, particularly core structural materials. In the present work, molecular dynamics method is used to investigate the interactions between edge dislocations and three typical irradiation-induced defects(void,Frank loop, and stacking fault tetrahedron) with the sizes of 3 nm, 5 nm, and 7 nm at different temperatures in Fe–10Ni–20Cr alloy. The critical resolved shear stresses(CRSSs) are compared among different defect types after interacting with edge dislocations. The results show that the CRSS decreases with temperature increasing and defect size decreasing for each defect type during the interaction with edge dislocations, except for the case of 3-nm Frank loops at 900 K. According to a comparison, the CRSS in Frank loop is significantly higher than that of others of the same size, which is due to the occurrence of unfaulting and formation of superjog or stacking-fault complex during the interaction. The atomic evolution of irradiation-induced defects after interacting with dislocations can provide a novel insight into the design of new structural materials.

Solid−solid phase transition of tungsten induced by high pressure:A molecular dynamics simulation

The phase transition of tungsten(W)under high pressures was investigated with molecular dynamics simulation.The structure was characterized in terms of the pair distribution function and the largest standard cluster analysis(LSCA).It is found that under 40−100 GPa at a cooling rate of 0.1 K/ps a pure W melt first crystallizes into the body-centred cubic(BCC)crystal,and then transfers into the hexagonal close-packed(HCP)crystal through a series of BCC−HCP coexisting states.The dynamic factors may induce intermediate stages during the liquid−solid transition and the criss-cross grain boundaries cause lots of indistinguishable intermediate states,making the first-order BCC−HCP transition appear to be continuous.Furthermore,LSCA is shown to be a parameter-free method that can effectively analyze both ordered and disordered structures.Therefore,LSCA can detect more details about the evolution of the structure in such structure transition processes with rich intermediate structures.

MD and OKMC simulations of the displacement cascades in nickel

The molecular dynamics(MD) method was used to investigate the displacement cascades with primary knock-on atom(PKA) energies of 2-40 keV at 100 and600 K.The migration energy of defects and their clusters was calculated by nudged elastic band(NEB) method.Object kinetic Monte Carlo(OKMC) was used to simulate the evolution of defects in Ni under annealing.In each annealing stage,the recombination mechanism was discussed and evolution of the defects under different cascade conditions was compared.It was found that the defects generated in high-temperature cascades are more stable than those in the low-temperature cascades.In addition,almost all the defects are annihilated during annealing process at low PKA energy.At PKA energy of 20-40 keV,however,a large number of defects would remain after annealing.

Simulation of radiation damages in molybdenum by combining molecular dynamics and OKMC

In this paper,radiation defects in bcc molybdenum with the primary knock-on atom(PKA) energies of2-40 keV are simulated by the molecular dynamics.The binding energy of single point defect-to-defect clusters increases with the cluster size.The stabiUty and mobility of point defects and defect clusters are analyzed.The interstitial-type clusters are found to be easily migrating along the <111> direction with low barriers(0.01-0.10 eV).Then,the object kinetic Monte Carlo is used to gain insight into the long-term defect evolution in the cascade.The simulation results indicate that Stage I almost occurs at annealing temperature of 100K,which corresponds to the correlated recombination resulting from the motion of small interstitial clusters(n ≤2).The formation of substage partly as result of the small vacancy clusters motion.At about 460 K,the Stage II starts because of uncorrected recombination due to an emitting mechanism of larger clusters.Size distribution of the clusters at the cascade quenching stage is positively correlated with the PKA energies,affecting notably the subsequent annealing process.

Strain and interfacial engineering to accelerate hydrogen evolution reaction of two-dimensional phosphorus carbide

Hydrogen,regarded as a promising energy carrier to alleviate the current energy crisis,can be generated from hydrogen evolution reaction(HER),whereas its efficiency is impeded by the activity of catalysts.Herein,effective strategies,such as strain and interfacial engineering,are imposed to tune the catalysis performance of novel two-dimensional(2D)phosphorus carbide(PC)layers using first-principle calculations.The findings show that P site in pristine monolayer PC(ML-PC)exhibits higher HER performance than C site.Intriguingly,constructing bilayer PC sheet(BL-PC)can change the coordinate configuration of P atom to form 3-coordination-P atom(3-co-P)and 4-coordination-P atom(4-co-P),and the original activity of 3-co-P site is higher than the 4-co-P site.When an external compressive strain is applied,the activity of the 4-co-P site is enhanced whereas the external strain can barely affect that of 3-co-P site.Interestingly,the graphene substrate enhances the overall activity of the BL-PC because the graphene substrate optimizes the?GH*value of 4-co-P site,although it can barely affect the HER activity of 3-co-P site and ML-PC.The desirable properties render 2 D PC-based material promising candidates for HER catalysts and shed light on the wide utilization in electrocatalysis.