Cr对Ni_3Al合金化效应的赝势平面波方法

Study on Alloying Effects of Ni_3Al with Cr Based on the Pseudopotential Plane-Wave Method

基于第一性原理赝势平面波方法研究了Cr加入Ni-Al合金后对Ni3Al几何和电子结构的影响,计算了不同强化相的晶胞总能量、形成热、结合能、费米能级下的成键电子数以及态密度、电荷密度,从不同角度出发,研究了不同强化相的稳定性。计算结果表明Ni-Al合金中添加Cr,Cr优先置换Al位且析出的新强化相较原强化相Ni3Al更为稳定,原因在于含Cr的新强化相在低能级处强烈成键,提高了其稳定性,其中Ni6Cr2最为稳定,但只在590℃下稳定存在,Ni5AlCr2、Ni6AlCr、Ni4Al2Cr2、Ni5Al2Cr稳定性依次降低。

Using the first-principle pseudopotential plane-wave method, the geometrical and electronic structure of Ni3Al with Cr additions were studied, the energy, heat of formation, cohesive energy and the number of bonding electron below Fermi energy were calculated, while, the density of states and charge were analysed. The stability of different strengthening phases was studied. The results show that Cr preferentially substitutes for the Al site in Ni3Al, and the new strengthening phases are stabler than Ni3Al, which is attributed to the stronger electronic interactions at lower energy level. Among all these phases, Ni6Cr2 is the stablest but it exists below 590 ℃, and NisAlCr2 and Ni6AlCr is stabler than Ni4Al2Cr2 and NisAl2Cr.