arXiv subjects

Piotr Zarzycki

Publications and source records attributed to Piotr Zarzycki.

4 recordsLinked to original sources

arXiv2026

Hydration-controlled twist forms a moir\'e glass in charge-frustrated layered silicates

Twisting layered materials produces moir\'e superlattices, but prescribed twist angles are usually obtained by demanding assembly procedures. Here we show that montmorillonite, an abundant swelling clay, forms tunable moir\'e superlattices naturally. Focal-series high-resolution transmission electron microscopy, geometric phase analysis, and molecular dynamics simulation reveal that its apparent rotational disorder is biased toward low-angle misorientations inherited from discrete hydration states. Multilayer stacks preferentially adopt twists near 1-2{\deg}, 4{\deg}, and 10{\deg}, producing long-wavelength moir\'es without long-range rotational order. We define this kinetically trapped state as a moir\'e glass, distinct from featureless turbostratic stacking. Simulations indicate that lattice-charge disorder stabilizes the angular preferences, whereas charge ordering promotes random stacking. Hydration screens interlayer interactions and lubricates twist, while dehydration arrests the resulting configurations in discrete steps. These results establish dynamic hydration as a macroscopic handle for programming twist in layered matter.

cond-mat.mtrl-sci↗

arXiv2026

Yukawa screening derivation of the bond-valence rule

The bond-valence model is a standard way to estimate bond strengths in crystals, but its exponential dependence on bond length has lacked a derivation from a specific physical interaction. We show that this form emerges as the leading-order limit of screened Coulomb electrostatics and that the fitted bond-valence softness can be interpreted in terms of an electronic screening length. This turns bond valence from an empirical fitting rule into a transferable descriptor of local screened charge response across coordination environments. The resulting theory predicts how the bond-valence parameters should vary with ionic charge and coordination number, and that prediction agrees with 150 fitted valences from 94 cation-oxygen species, including 68 in fourfold coordination and 82 in sixfold coordination, at an abundance-weighted coefficient of determination of 0.986. A comparison with first-principles charge densities shows that the bond-valence shell radius tracks the electronic screening cloud with coefficients of determination of 0.9998 for ten alkali and alkaline-earth oxides and 0.967 for 21 other binary oxides whose nearest-neighbor environments match the theory's assumptions. The widely used bond-valence model is thus the leading-order expression of screened electrostatics in ionic solids.

cond-mat.mtrl-sci↗

arXiv2022

Machine Learning in Heterogeneous Porous Materials

The "Workshop on Machine learning in heterogeneous porous materials" brought together international scientific communities of applied mathematics, porous media, and material sciences with experts in the areas of heterogeneous materials, machine learning (ML) and applied mathematics to identify how ML can advance materials research. Within the scope of ML and materials research, the goal of the workshop was to discuss the state-of-the-art in each community, promote crosstalk and accelerate multi-disciplinary collaborative research, and identify challenges and opportunities. As the end result, four topic areas were identified: ML in predicting materials properties, and discovery and design of novel materials, ML in porous and fractured media and time-dependent phenomena, Multi-scale modeling in heterogeneous porous materials via ML, and Discovery of materials constitutive laws and new governing equations. This workshop was part of the AmeriMech Symposium series sponsored by the National Academies of Sciences, Engineering and Medicine and the U.S. National Committee on Theoretical and Applied Mechanics.

cs.LG↗

arXiv2008

The effect of pressure and spin on the isotopic composition of ferrous iron dissolved in periclase and silicate perovskite

We perform density functional calculations of the equilibrium 57Fe/54Fe ratios for ferrous iron dissolved in periclase and MgSiO3 perovskite at the pressures and temperatures of the Earth's mantle. Pressure increases the partitioning of 57Fe into both phases by a factor of three from the Earth's surface to the core-mantle boundary. In ferropericlase, a large contribution to this increase comes from the electronic transition from high-spin to low-spin iron. Our calculations demonstrate that pressure-induced fractionation can play a major role in determining planetary iron-isotope composition.

cond-mat.mtrl-sci↗