Disorder and electron correlation effects in the ground state of Ni-Co-Mn-Sn alloys with Heusler structures*

We consider ab-intio calculations of Co-doped Ni-Mn-Sn shape memory alloy. The Co doping leads to a decrease in both the martensitic transformation temperature and the Curie temperature of martensite and to an increase in the Curie temperature of austenite. Besides, large magnetisation changes occur in the vicinity of structural transformation. As a result, the tuning of Co and Mn contents can lead to favorable magnetocaloric properties . In this work, we focus on the effect of atomic disorder and electron correlation on the structural, magnetic and electronic properties of Ni-Co-Mn-Sn systems by using the Density Functional Theory (DFT) implemented in the VASP and SPR-KKR packages within a 32-atom supercell and the coherent potential approximation, respectively. The optimized atomic positions for compositions studied are obtained by the USPEX package. To study the effect of exchange-correlation, a series of ground state calculations were performed using both the GGA-PBE functional and Meta-GGA with SCAN functional of DFT.