CAJ | 학술논문

采用基于密度泛函理论的第一性原理方法,分别研究了压力作用下Fe从体心立方(bcc,α相)结构到六角密排(hcp,ε相)结构相变的两种不同的相变机理:相变过程中出现亚稳定的面心立方(fcc)结构(bcc-fcc-hcp),以及相变过程中没有出现亚稳定的fcc结构(bcc-hcp).计算结果表明:静水压力条件下,相变过程中并不会产生亚稳定的fcc结构,这与最近的原位XRD实验测量结果相一致.随着压力的增加, fcc-hcp的相变势垒逐渐增加,压力趋向于阻止Fe从fcc结构到hcp结构的相变.计算得到了相变过程中原子磁性和结构的详细信息,分析表明相变过程中涉及复杂的磁性转变,并且讨论了原子磁性对结构转变影响的物理机理.此外,对分子动力学模拟中产生亚稳定的fcc结构的原因也进行了讨论.
채용기우밀도범함이론적제일성원리방법,분별연구료압력작용하Fe종체심립방(bcc,α상)결구도륙각밀배(hcp,ε상)결구상변적량충불동적상변궤리:상변과정중출현아은정적면심립방(fcc)결구(bcc-fcc-hcp),이급상변과정중몰유출현아은정적fcc결구(bcc-hcp).계산결과표명:정수압력조건하,상변과정중병불회산생아은정적fcc결구,저여최근적원위XRD실험측량결과상일치.수착압력적증가, fcc-hcp적상변세루축점증가,압력추향우조지Fe종fcc결구도hcp결구적상변.계산득도료상변과정중원자자성화결구적상세신식,분석표명상변과정중섭급복잡적자성전변,병차토론료원자자성대결구전변영향적물리궤리.차외,대분자동역학모의중산생아은정적fcc결구적원인야진행료토론.
We perform ab initio calculations on two different transition mechanisms of the bcc-to-hcp phase transition in Fe under pressure distinguished by the occurrence of the metastable fcc intermediate phase on the transition path, that is, the bcc-hcp and the bcc-fcc-hcp. The calculated results indicate that the occurrence of the fcc intermediate state during the transition is energetically unfavorable, which is consistent with the recent in situ XRD experiments. The enthalpy barrier of the fcc-hcp increases with pressure increasing, which indicates that the pressure tends to impede the transformation from fcc to hcp phase in Fe. The details of the structural and magnetic behaviors of the intermediate states during the transition are investigated, which indicates that there are complex magnetism transitions during the phase transition. The physical origins of the influence of magnetism on the phase transition are discussed. Moreover, the origin of the occurrence and evolution of the fcc metastable structure during the transition in the MD simulations are also discussed.