The martensitic-type phase transformation paths from the rutile to theα-PbO2 phase of TiO2 are studied with linear interpolation and NEB/G-SSNEB methods based on first-principles calculations.Its potential energy sur...The martensitic-type phase transformation paths from the rutile to theα-PbO2 phase of TiO2 are studied with linear interpolation and NEB/G-SSNEB methods based on first-principles calculations.Its potential energy surface and the lowest energy path are revealed.Our results indicate that the titanium atoms of the rutile phase shuffle along the[0-11]rut crystal direction to form theα-PbO2 phase.During the phase transition,the oxygen atoms are dragged by the heavier titanium atoms and then reach their new equilibrium positions.The barrier of phase transition from nudged elastic band theory is about 231 meV,which is qualitatively consistent with previous theoretical calculations from the monoclinic phase to the tetragonal phase for ZrO2 and HfO2.Debye model can also be successfully used to predict the pressure and temperature of the phase transformation.展开更多
We derived revised effective diffusion energy barriers following the Boltzmann distribution assumption for impurity atoms in a bulk material under the impact of various kinds of point defects to reveal the insights of...We derived revised effective diffusion energy barriers following the Boltzmann distribution assumption for impurity atoms in a bulk material under the impact of various kinds of point defects to reveal the insights of migration mechanisms. The effective diffusion energy barriers of copper impurities in bulk zirconium were calculated through the first principle method under the presented hypothesis. Our results(?E_(||) =1.27 eV, ?E_⊥=1.31 eV) agreed well with the experimental results(?E_(||) =1.54 eV, ?E_⊥=1.60 eV), which validated bulk diffusion as the major mechanism for copper diffusion in zirconium. The effective diffusion energy barriers could be used for estimating whether the defects will accelerate the diffusion or slow them down by acting as traps of the impurity atoms. On the other hand, the first principle results of the impurity diffusion via defects could be further used as inputs of larger scale computational simulations, such as MC(Monte Carlo) or Phase Field calculations.展开更多
Using Embedded-atom-method (EAM) potential, we have performed in detail molecular dynamics studies on a Fe adatom adsorption and diffusion dynamics on three low miller index surfaces, Fe (110), Fe (001), and Fe (111)....Using Embedded-atom-method (EAM) potential, we have performed in detail molecular dynamics studies on a Fe adatom adsorption and diffusion dynamics on three low miller index surfaces, Fe (110), Fe (001), and Fe (111). Our results present that adatom adsorption energies and diffusion barriers on these surfaces have similar monotonic trend: adsorption energies, Ea(110) Ea(001) Ea(111), diffusion barriers, Ed(110) Ed(001) Ed(111). On the Fe (110) surface, adatom simple jump is the main diffusion mechanism with relatively low energy barrier;nevertheless, adatoms exchange with surface atoms play a dominant role in surface diffusion on the Fe (001).展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51872227,51572219,and 11447030).
文摘The martensitic-type phase transformation paths from the rutile to theα-PbO2 phase of TiO2 are studied with linear interpolation and NEB/G-SSNEB methods based on first-principles calculations.Its potential energy surface and the lowest energy path are revealed.Our results indicate that the titanium atoms of the rutile phase shuffle along the[0-11]rut crystal direction to form theα-PbO2 phase.During the phase transition,the oxygen atoms are dragged by the heavier titanium atoms and then reach their new equilibrium positions.The barrier of phase transition from nudged elastic band theory is about 231 meV,which is qualitatively consistent with previous theoretical calculations from the monoclinic phase to the tetragonal phase for ZrO2 and HfO2.Debye model can also be successfully used to predict the pressure and temperature of the phase transformation.
基金Science Challenge Project(TZ2016003-1-105)CAEP Microsystem and THz Science and Technology Foundation(CAEPMT201501)National Basic Research Program of China(2011CB606405)。
基金Funded in Part by National Natural Science Foundation of China(Nos.11575129 and 11275142)
文摘We derived revised effective diffusion energy barriers following the Boltzmann distribution assumption for impurity atoms in a bulk material under the impact of various kinds of point defects to reveal the insights of migration mechanisms. The effective diffusion energy barriers of copper impurities in bulk zirconium were calculated through the first principle method under the presented hypothesis. Our results(?E_(||) =1.27 eV, ?E_⊥=1.31 eV) agreed well with the experimental results(?E_(||) =1.54 eV, ?E_⊥=1.60 eV), which validated bulk diffusion as the major mechanism for copper diffusion in zirconium. The effective diffusion energy barriers could be used for estimating whether the defects will accelerate the diffusion or slow them down by acting as traps of the impurity atoms. On the other hand, the first principle results of the impurity diffusion via defects could be further used as inputs of larger scale computational simulations, such as MC(Monte Carlo) or Phase Field calculations.
文摘Using Embedded-atom-method (EAM) potential, we have performed in detail molecular dynamics studies on a Fe adatom adsorption and diffusion dynamics on three low miller index surfaces, Fe (110), Fe (001), and Fe (111). Our results present that adatom adsorption energies and diffusion barriers on these surfaces have similar monotonic trend: adsorption energies, Ea(110) Ea(001) Ea(111), diffusion barriers, Ed(110) Ed(001) Ed(111). On the Fe (110) surface, adatom simple jump is the main diffusion mechanism with relatively low energy barrier;nevertheless, adatoms exchange with surface atoms play a dominant role in surface diffusion on the Fe (001).
