Possible Martensitic Transformation In Heusler Alloy Pt-Mn-Sn From First Principles

In recent years,people's living standards and demands have greatly increased,and existing materials have not been able to meet people's needs.What we want to study is one of the most representative alloys--materials with shape memory effects.Among them,ferromagnetic shape memory alloys?FSMAs?are highly valued.Because this new type of functional material exhibits various excellent properties under the action of a magnetic field.These excellent physical properties make FSMAs have potential application value in many fields.In this work,the first-principles calculation method based on the density functional theory is used.Firstly,the tetragonal distortion graph of the Heusler-type Pt₂MnSn is drawn.Based on the energy change,the electronic structure and magnetic properties are combined to predict the possibility of martensitic transformation;Then,we also plotted the tetragonal distortion graph of Mn₂PtSn.According to the energy change curve,combined with the electronic structure and magnetic calculation results,we predicted the possibility of martensitic transformation.The main results of our work are as follows:1.First,the lattice constant of the Pt₂Mn Sn cubic phase must be determined.We give the changes in the energy of the FM and PM about L2₁ and Hg₂CuTi structures of Pt₂MnSn with lattice constants,respectively.The results show that the total energy of the ferromagnetic state of the L2₁ structure is the lowest,indicating that the stable structure of Pt₂MnSn austenite is the L2₁ ferromagnetic structure.2.In order to predict whether Pt₂MnSn can occur martensitic transformation,based on the first-principles method,the CASTEP module was used to calculate the tetragonal distortion of the L2₁ structure of Pt₂MnSn.Calculated,the energy minimum appears at c/a=0.84,and the energy difference between the minimum and cubic phase is as high as 107mev/f.u.Therefore,from the thermodynamic point of view,Pt₂MnSn may occur martensitic transformation,and the electronic structure of the cubic phase also shows this point.Besides,both the cubic and tetragonal phases of Pt₂MnSn are ferromagnetic structures and their total magnetic moments are 4.26?_B and 4.12?_B,respectively.3.In order to predict whether Mn₂PtSn can occur martensitic transformation,we need to determine its lattice structure through geometric optimization firstly,and then to calculate the tetragonal distortion.After calculation,the energy minimum of Mn₂PtSn appears at c/a=1.28,and the energy difference between the minimum and cubic phase is as high as 101mev/f.u.From the magnetic structure calculation results,we can see that both cubic and tetragonal phases of Mn₂Pt Sn are antiferromagnetic structures and their total magnetic moments are 0.20?_B and-0.02?_B,respectively.After analyzing the electronic structure of Mn₂PtSn,the structural stability of the Mn₂PtSn alloy is greatly enhanced after the martensite transformation.Therefore,we predict that Mn₂PtSn may occur martensitic transformation.