合金碳化物（Fe,Mo）3C的磁性及磁致热力学性质

Magnetism and magnetic-field-induced thermodynamic properties of alloy carbides （Fe,Mo）3C

利用基于第一性原理的VASP软件计算钢中合金碳化物(Fe,Mo)3C在0 K、0 Pa的磁矩和形成能,利用热力学平衡软件MTDATA计算合金碳化物(Fe,Mo)3C的化学自由能改变量,利用Weiss分子场理论计算合金碳化物在12 T强磁场下的磁自由能改变量。结果表明,合金碳化物(Fe,Mo)3C的磁矩主要来源于不同Wyckoff位置的Fe原子,8d位置的Fe原子对磁矩的影响比4c位置的Fe原子更大,而Mo原子会使合金碳化物的磁矩降低;合金碳化物Fe 2MoC、Mo 3C的形成能为负,表明这两种合金碳化物比Fe 3C和FeMo 2C更稳定;另外,Mo原子会降低合金碳化物(Fe,Mo)3C化学自由能改变量,增大其磁自由能改变量。

By employing the first-principles-basd software VASP,the magnetic moment and forming energy of alloy carbides(Fe,Mo)3C at 0 K and 0 Pa were calculated.Besides,the chemical Gibbs free energy change as well as magnetic Gibbs free energy change under a 12 T high-intensity megnetic field were calculated by thermodynamic equilibrium software MTDATA and Weiss molecular field theory,respectively.The results show that the magnetic moment of alloy carbides(Fe,Mo)3C is mainly derived from Fe atoms at different Wyckoff positions.Fe atoms at 8d position have a greater influence on the magnetic moment than Fe atom at 4c position,while Mo atom would cause the decrease of magnetic moment of(Fe,Mo)3C.The formation energy of alloy carbides Fe 2MoC and Mo 3C is negative,indicating that these two carbides are more stable than Fe 3C and FeMo 2C.Moreover,higher Mo concentration in carbides leads to the decrease of chemical Gibbs free energy change and the increase of magnetic Gibbs free energy change.