Triaxial-Stress-Induced Homogeneous Hysteresis-Free First-Order Phase Transformations with Stable Intermediate Phases

Levitas, Valery I.; Chen, Hao; Xiong, Liming

doi:10.1103/physrevlett.118.025701

Cited by 42 publications

(62 citation statements)

References 35 publications

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“…This potential has been demonstrated to be successful in describing the crystal structure transition from the diamond-cubic to β-Sn in single crystal silicon (Si I to Si II) under a uniaxial stress of ∼12GPa (see [22] and current results), which is close to the experimental value [23]. Advantage of the the Tersoff interatomic potential for the description of Si I to Si II PT in comparison with four other potentials is demonstrated in [24]. The majority of simulations have been performed for a Si sample containing 64,000 atoms.…”

Section: Simulation Methodssupporting

confidence: 74%

Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion

2017

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A conceptually novel continuum/atomistic approach for predicting lattice instability during crystal-crystal phase transformations (PTs) is developed for the general loading with an arbitrary stress tensor and large strains. It is based on the synergistic combination of the generalized Landau-type theory for PTs and molecular dynamics (MD) simulations. The continuum approach describes the entire dissipative transformation process in terms of an order parameter, and the general form of the instability criterion is derived utilizing the second law of thermodynamics. The feedback from MD allowed us to present the instability criterion for both direct and reverse PTs in terms of the critical value of the modified transformation work, which is linear in components of the true stress tensor. It was calibrated by MD simulations for direct and reverse PTs between semiconducting silicon Si I and metallic Si II phases under just two different stress states. Then, it describes hundreds of MD simulations under various combinations of three normal and three shear stresses. In particular, the atomistic simulations show that the effects of all three shear stresses along cubic axes on lattice instability of Si I are negligible, which is in agreement with our criterion.

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Section: Simulation Methodssupporting

confidence: 74%

Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion

2017

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“…There is an infinite number (continuum) of the homogeneous intermediate phases along the homogeneous Si I↔Si II path which are in indifferent thermodynamic equilibrium. These results are in good agreement with the MD results in Levitas et al (2017a). The effect of the hysteresis width of the nanostructure evolution and the distribution of the driving force for PT was analyzed in Section 5.…”

Section: Introductionsupporting

confidence: 82%

“…7, despite considering a heterogeneous initial perturbation for the order parameter, the system undergoes a unique homogeneous and hysteresis-free first order PT with no nucleation and two-phase band formation and growth. The same behavior was observed in MD simulations for Si I↔Si II PTs for such stress states at which the instability lines for direct and reverse PTs coincide (Levitas et al (2017a)). To give a simple geometric and energetic interpretation of this phenomenon, we consider small strains and will operate with the Gibbs energy per unit volume for homogeneous states G(σ σ σ, η, θ) = ψ(ε ε ε, η, θ) − σ σ σ: : :ε ε ε, the same as what was done in Levitas and Preston (2002a).…”

Section: Accepted Manuscriptsupporting

confidence: 73%

Phase-field approach for stress- and temperature-induced phase transformations that satisfies lattice instability conditions. Part 2. simulations of phase transformations Si I↔Si II

Babaei

Levitas

2018

International Journal of Plasticity

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“…This seemed to be impossible due to the large number of combinations, but unexpected guidance came from the PT criterion analytically formulated within the large-strain phase field approach (PFA) 33) under action of all six stresses · ij . Molecular dynamics simulations 34,35) and the first-principle simulations 36) were then performed to find lattice instability conditions for cubic-totetragonal PT between diamond cubic phase Si I and metallic phase Si II, in both directions. The results for Si I ¼ Si II PT obtained with molecular dynamics and first-principle simulations are quite close.…”

Section: Crystal Lattice Instability Criteria: Phase Fieldmentioning

confidence: 99%

“…Phase transformation criteria in terms of stress · 3 vs. · 1 = · 2 for direct (D) Si I-to-Si II and reverse (R) Si II-to-Si I phase transformations from the first-principle simulations and molecular dynamics simulations,34,35) as well as the metallization criterion from the first-principle simulations. This figure is reproduced with permission from Ref 36…”

mentioning

confidence: 99%

High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils

Levitas

2019

Mater. Trans.

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Numerous experiments have documented that combination of severe plastic deformation and high mean pressure during high-pressure torsion in rotational metallic, ceramic, or diamond anvils produces various important mechanochemical effects. We will focus here on four of these: plastic deformation (a) significantly reduces pressure for initiation and completion of phase transformations (PTs), (b) leads to discovery of hidden metastable phases and compounds, (c) reduces PT pressure hysteresis, and (d) substitutes a reversible PT with irreversible PT. The goal of this review is to summarize our current understanding of the underlying phenomena based on multiscale atomistic and continuum theories and computational modeling. Recent atomistic simulations provide conditions for initiation of PTs in a defect-free lattice as a function of the general stress tensor. These conditions (a) allow one to determine stress states that significantly decrease the transformation pressure and (b) determine whether the given phase can, in principle, be preserved at ambient pressure. Nanoscale mechanisms of phase nucleation at plastic-strain-induced defects are studied analytically and by utilizing advanced phase field theory and simulations. It is demonstrated that the concentration of all components of the stress tensor near the tip of the dislocation pileup may decrease nucleation pressure by a factor of ten or more. These results are incorporated into the microscale analytical kinetic equation for strain-induced PTs. The kinetic equation is part of a macroscale geometrically-nonlinear model for combined plastic flow and PT. This model is used for finite-element simulations of plastic deformations and PT in a sample under torsion in a rotational anvil device. Numerous experimentally-observed phenomena are reproduced, and new effects are predicted and then confirmed experimentally. Combination of the results on all four scales suggests novel synthetic routes for new or known high-pressure phases (HPPs), experimental characterization of strain-induced PTs under high-pressure during torsion under elevated pressure.

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Triaxial-Stress-Induced Homogeneous Hysteresis-Free First-Order Phase Transformations with Stable Intermediate Phases

Cited by 42 publications

References 35 publications

Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion

Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion

Phase-field approach for stress- and temperature-induced phase transformations that satisfies lattice instability conditions. Part 2. simulations of phase transformations Si I↔Si II

High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils

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