| Nowadays,there are comprehensive and complete scientific methods to study the properties of materials at macro-scale,but for nanomaterials,because of its micro-scale and experimental phenomena are difficult to observe,many aspects of research are still in its infancy.Gallium nitride sphalerite has excellent physical and chemical properties,which attracts the eyes of many scientists.It is one of the representatives of the thirdgeneration semiconductor materials,which has significant applications in the field of aeronautics and astronautics.Understanding the mechanical properties of materials is the basis for designing and using materials,but the study about the mechanical properties of B3-GaN is insufficient,many studies also focus on its electronic and optical properties.In this paper,we use molecular dynamics simulation to study the mechanical properties of B3-GaN in detail.We have studied the material deformation of B3-GaN under nanoindentation.By the P-h curve of the(001)plane nanoindentation experiment,we can find that B3-GaN releases a large number of dislocations in the plastic deformation stage.All of these dislocations are perfect dislocations with Burgers vector b =1/2 <110>.With the increase of indentation depth,a large number of dislocations attached to the indentation region will form dislocation loops during the movement of dislocations,which will fall off from the indentation region and emit into the material.The results show that Mises stress field tends to be uniformly distributed along the 45odirection,because dislocation will start on the slip surface which is the easiest to slip.We also studied the effect of temperature on the strength of B3-GaN,and found that temperature has an effect on B3-GaN,and the strength of materials is higher at lower temperatures.In addition,we also studied the anisotropy of B3-GaN crystals,and found that the initial stage of plastic deformation on three indentation surfaces is different.The(111)plane has the maximum hardness.Under indentation simulation of different orientation planes,dislocation density is different.The size factor of plastic zone in B3-GaN is similar to that in FCC metal.We have studied the formation process of prismatic dislocation loops and found two kinds of the formation mechanism of prismatic dislocation loops.One is similar to the "lasso"-like mechanism.The two shear loops attached to the indentation area will be close to each other first,then separated.The two screw components of the shear loops attract and close to each other,and then annihilate,forming a prismatic dislocation loop and falling off.The other can be called the extended "lasso"-like mechanism,the two screw components of a shear loop will move to another shear loop,and then the two screw components will keep approaching,eventually meet and react,and fall off from the shear loop to form a prismatic dislocation loop.We also studied twin B3-GaN crystal and investigated the effect of twin boundary on the properties of multilayer materials.We also found a relationship between the hardness of the material and the thickness of the layer.When the thickness of the multilayers is about 46.8 ?,the hardness of the multilayers is the highest,the twin boundary affects the properties of the material.Through IDS and the distribution of stress field,when the layer thickness is less than a certain value,it can be found that the interface does not impede the dislocation. |
