Magnetic Cluster Expansion Of Fe-Cr Alloy By Monte Carlo Simulation

Phase change is the process by which the material system transitions from one phase to another.The internal spin of ferromagnetic at low temperature exhibits an ordered arrangement.When the temperature exceeds the critical value,the order of rotation is destroyed,and then the ferromagnet is converted into a paramagnetic state.The rapid development of computer technology,ferromagnetic phase transition model continues to improve.The magnetic cluster expansion model is an effective method taking into account the magnetic moments of atoms and the position of atoms in the alloy.This method can be applied to all sizes of clusters.Fe-Cr alloy is studied in this paper.The magnetic cluster expansion model of Fe-Cr binary alloy magnetic phase transition is systematically studied.Understand the binary alloy,and from the microscopic point of view of the basic principle of ferromagnetic phase transition.The main contents and research results of this paper are as follows:(1)The establishment of magnetic cluster model based on Monte Carlo,using plane wave pseudopotential method of density functional theory of the VASP program that the parameters based on the simulation results are compared with the exact values or related documents,to verify the effectiveness of the numerical simulation method(2)With the relationship between Cr content and Curie point magnetic cluster model to study the state of disorder in the low Cr content(0-10%),the Curie temperature increased,in the Cr content of about 6% reach the maximum,with the Cr content increases,and gradually reduced.(3)With the Cr content in the magnetic clusters of Fe-Cr alloy and the enthalpy model system in low component,the mixing enthalpy is negative,the stable structure of Fe-Cr alloy;enthalpy of mixing with the increase of Cr,the first decreased and then increased,reaching a minimum value at Cr6%,this structure is most stable when the composition;at about 12%,the enthalpy of mixing the sign is positive,so the trend of phase separation.(4)With Curie on the relationship between Cr content and magnetic cluster model of ordered state,and ordered and disordered comparison,obtained in the same component in the sample,the Curie temperature is higher than that of the ordered structure disordered samples,especially in the 6% samples of the biggest difference.Compared with the ordered structure,the probability of the formation of clusters of Cr atoms in disordered states is increased,and the antiferromagnetic interaction between Cr-Cr can partially offset the magnetic moment,thus reducing the phasetransition temperature.(5)Based on the phase diagram calculation method of magnetic cluster model,the phase transition of alpha-gamma and gamma-ray is calculated.