arXiv subjects

Antonino Marco Saitta

Publications and source records attributed to Antonino Marco Saitta.

5 recordsLinked to original sources

arXiv2026

Screening strongly correlated materials in solid oxide cells with quantum simulation

We develop an end-to-end framework for assessing a quantum-computing application in industrial materials science: the screening of strongly correlated oxygen-electrode materials for SOFCs and SOECs. We formulate the materials problem in terms of interface observables including oxygen-vacancy formation energies, vacancy migration barriers, and electronic conductivity. We describe how these observables can be obtained using a diagrammatic GW-based embedding, either GW+DMFT or self-energy embedding theory (SEET), applied to a DFT-screened shortlist. The atomistic electrode/electrolyte interface defines the electronic structure problem from which the correlated impurity models are constructed. Quantum impurity solvers would provide the finite-temperature impurity Green's functions required by the embedding. The computational challenges that classical solvers may encounter as the interacting active space grows, together with the polynomial scaling of quantum Hamiltonian simulation for efficiently represented discretized models, open an opportunity for quantum advantage. We identify the benchmarks needed to assess this opportunity through convergence of vacancy and migration energetics and comparison with the best applicable classical solvers. We provide illustrative logical qubit counts and identify the thermal state preparation, simulation, measurement, and repeated-solve costs needed for a complete resource assessment. We connect microscopic observables to macroscopic engineering metrics using a continuum model for mixed ionic--electronic conducting oxygen electrodes that couples oxygen surface exchange, solid-state oxygen transport, electrode microstructure, and finite electrode thickness. Finally, we estimate the potential worldwide business value of improved electrode materials under SOFC and SOEC deployment scenarios informed by public technical targets and electrolyser deployment data.

quant-ph↗

arXiv2023

Thermal dependence of the hydrated proton and optimal proton transfer

Water is a key ingredient for life and plays a central role as solvent in many biochemical reactions. However, the intrinsically quantum nature of the hydrogen nucleus, revealing itself in a large variety of physical manifestations, including proton transfer, gives rise to unexpected phenomena whose description is still elusive. Here we study, by an unprecedented combination of state-of-the-art quantum Monte Carlo methods and path-integral molecular dynamics, the structure and hydrogen-bond dynamics of the protonated water hexamer, the fundamental unit for the hydrated proton. We report a remarkably low thermal expansion of the hydrogen bond from zero temperature up to 300 K, owing to the presence of short-Zundel configurations, characterised by proton delocalisation and favoured by the synergy of nuclear quantum effects and thermal activation. The hydrogen bond strength progressively weakens above 300 K, when localised Eigen-like configurations become relevant. Our analysis, supported by the instanton statistics of shuttling protons, reveals that the near-room-temperature range from 250 K to 300 K is a ``sweet spot'' for proton transfer, and thus for many phenomena depending on it, including life.

cond-mat.mtrl-sci↗

arXiv2021

Free energy calculations and unbiased dynamics reveal a continuous liquid-liquid transition in water no man's land

The existence of a first-order phase transition between a low-density liquid (LDL) and a high-density liquid (HDL) forms of supercooled water has been a central and highly debated issue of physics and chemistry in the last three decades. We present a computational study that allows to determine the free-energy landscapes of supercooled water over a wide range of pressure and temperature conditions, using the accurate TIP4P/2005 force field. Our approach combines topology-based structural transformation coordinates, state-of-the-art free-energy calculation methods, and extensive unbiased molecular dynamics simulations. All our results indicate that transitions between the LDL and HDL forms are smooth throughout the so-called "no man's land", and that free-energy barriers do not appear until the onset of the solid, non-diffusive amorphous forms.

cond-mat.soft↗

arXiv1998

Effects of disorder on the optical properties of the (Zn,Mg)(S,Se) quaternary alloy

The electronic and optical properties of (Zn,Mg)(S,Se) wide-gap solid solutions are studied using ab initio techniques and starting from the previously determined atomistic structure of the alloy. Compositional disorder is shown to close substantially the gap with respect to the predictions of the virtual-crystal approximation. The bowing of the fundamental gap vs. composition predicted by our calculations is in very good agreement with experiments available for the Zn(S,Se) pseudo-binary alloy. At temperatures typical for MBE growth, the quaternary alloy displays a rather large amount of short-range order whose effect is to slightly but unmistakably open the gap. Our results agree well with recent experimental data for the quaternary alloy.

cond-mat.mtrl-sci↗

arXiv1997

Structural and Electronic Properties of a Wide-gap Semiconductor Alloy: Zn_xMg_{1-x}S_ySe_{1-y}

The structural properties of the $Zn_xMg_{1-xS_ySe_{1-y}}$ solid solutions are determined by a combination of the computational alchemy and the cluster expansion methods with Monte Carlo simulations. We determine the phase diagram of the alloy and show that the homogeneous phase is characterized by a large amount of short-range order occurring among first-nearest neighbors. Electronic-structure calculations performed using the special quasi-random structures approach indicate that the energy gap of the alloy is rather sensitive to this short-range order.

cond-mat.mtrl-sci↗