Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2508.14721

Severe plastic deformations, mechanochemistry, and microstructure evolution under high pressure: In Situ Experiments, Four-Scale Theory, New Phenomena, and Rules

Valery I. Levitas
View original source ↗Read source document ↗Export metadata ↓

Abstract

Processes involving severe plastic deformations (SPD) and phase transformations and chemical reactions (PTs/CRs) under high pressures are widespread for obtaining new nanostructured phases and their processing, mechanochemical synthesis, military applications, and nature. SPD strongly reduce the pressure required for PTs/CRs (by one-two orders of magnitude) and PT hysteresis; lead to hidden metastable phases, which cannot be obtained otherwise, and substitute reversible PTs/CRs with irreversible ones. This review is devoted to breakthroughs in understanding multifaceted interactions between high-pressure PTs/CRs, SPD, and microstructure evolution from the viewpoint of advanced mechanics and thermodynamics of materials under stress and plastic strain tensors. A novel concept of plastic strain-induced PTs/CRs under high pressure is explored using four-scale theory and simulations (from atomistic to nano- and scale-free phase-field approaches to macroscale) coupled to in situ experiments in traditional and rotational diamond anvil cells, and their integration. Its development revealed various phenomena and misinterpretations, resolved numerous puzzles, found the first general rules in these fields, and suggested ways for economic defect-induced synthesis of high-pressure phases and nanostructures. Coupled analytical/computational/experimental approaches are developed for complete characterization of occurring processes and finding all heterogeneous scalar and tensorial fields. Applications include high-pressure torsion, surface treatment, high-pressure tribology, PTs/CRs in shear bands leading to severe transformation/reaction-induced plasticity and self-blown-up processes, mechanisms of deep-focus earthquakes, the appearance of microdiamonds in low-pressure-temperature Earth crust, and the mechanochemical origin of life beyond Earth. Unresolved problems and future directions are outlined.

Explore related subjects

cond-mat.mtrl-sci

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Valery I. Levitas. 2025-08-20. Severe plastic deformations, mechanochemistry, and microstructure evolution under high pressure: In Situ Experiments, Four-Scale Theory, New Phenomena, and Rules. https://arxiv.org/abs/2508.14721

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Incommensurate structural and magnetic modulations in potassium-rich cryptomelane, K$_x$Mn$_8$O$_{16}$ ($x\approx1.45$)

Cryptomelane is a hollandite-like material consisting of K$^+$ cations in an $α$-MnO$_2$ tunnel-like crystallographic motif. Cryptomelane with stoichiometry K$_x$Mn$_8$O$_{16}$ ($x\approx1.45$) has been synthesized and its magnetic properties investigated using variable-temperature magnetic susceptibility, heat capacity, and neutron powder diffraction. Three distinct transitions at $T_1=184$\,K, $T_2=54.5$\,K, and $T_3=24$\,K are observed. At $T_1$ there is a subtle tetragonal$\rightarrow$monoclinic transition associated with emergence of a set of non-magnetic superstructure peaks indexable to a $\vec{k}_\mathrm{struc}\approx0.74\vec{c^*}$ incommensurate modulation parallel to the $α$-MnO$_2$ tunnels. Our findings are consistent with a relation previously reported in titanate hollandites, that $x\approx2|\vec{k}_\mathrm{struc}|$. Magnetic Bragg peaks emerge below $T_2=54.5$\,K, and their positions indicate an incommensurate modulated magnetic structure. The model consistent with the data is a dual-$\vec{k}_\mathrm{mag}$ structure with a ferromagnetic $|\vec{k}_\mathrm{mag}|=0$ component and an incommensurate $\vec{k}_\mathrm{mag}\approx0.37\vec{c^*}$, with the latter most likely to be helical. The period of oscillation of the incommensurate magnetic component is in line with predictions based on a Heisenberg spin Hamiltonian [Mandal \textit{et al}. Phys. Rev. B 90, 104420 (2014)]. Below $T_3=24$\,K, there is a magnetic transition, which gives rise to a different set of magnetic Bragg peaks indicative of a highly complex magnetic structure.

cond-mat.mtrl-sci↗
arXiv2026

An anisotropic functional for two-dimensional material systems

Density function theory is the workhorse of modern electronic structure theory. However, its accuracy in practical calculations is limited by the choice of the exchange-correlation potential. In this respect, two-dimensional materials pose a special challenge, as all these materials and their heterostructures have a crucial similarity. The underlying atomic structures are strongly spatially inhomogeneous, implying that current exchange-correlation functionals, that in almost all cases are isotropic, are ill-prepared for an accurate description. We present an anisotropic screened-exchange potential, that remedies this problem and reproduces the band-gap of 2D materials as well as the piecewise linearity of the total energy with fractional occupation number.

cond-mat.mtrl-sci↗
arXiv2026

Thermally-driven reorientation of the Néel vector in altermagnetic MnTe

Altermagnets are novel magnetic systems that possess a spin-polarized electronic band structure without a net magnetic moment, making them promising for device applications. Hexagonal MnTe, a prototypical altermagnet, arguably exhibits the most properties consistent with theoretical predictions, including an anomalous Hall effect despite a vanishing net magnetization, and altermagnetinduced electronic band splitting. However, fundamental questions remain, including why some effects only appear significantly below the magnetic ordering temperature. Here, we resolve this discrepancy by revealing a reorientation of the Néel vector in single-crystalline MnTe. The Néel vector points 30° from the a-axis at low $T$, before aligning directly with the a-axis around $T\simeq 260$ K. We attribute this to single-ion anisotropy, which depends on temperature-dependent lattice parameters. We obtained these results using muon-spin spectroscopy, magnetization measurements, and X-ray diffraction; we show that the findings are consistent with neutron diffraction. Manipulating this effect, for example through strain, could unlock sensitive electronic detection schemes for external stimuli, paving the way for functional altermagnetic devices.

cond-mat.mtrl-sci↗