arXiv subjects

Frank Cerasoli

Publications and source records attributed to Frank Cerasoli.

4 recordsLinked to original sources

arXiv2026

Stability and superstructural ordering of alkali-triel-pnictide clathrates A$_8$T$_{27}$Pn$_{19}$

Clathrates are a class of inclusion compounds that offer various useful and surprising phenomena, including superconductivity, thermoelectricity, and the potential for high-density ion storage. Stability conditions within the Alkali-Triel-Pnictide A$_8$T$_{27}$Pn$_{19}$ family of unconventional clathrates are investigated with high-throughput density functional theory calculations, establishing trends in formation energy, structural and electronic properties. Electronic structure calculations and first-principles molecular dynamics simulations show that the ionization potential of guest alkaline atoms strongly influences the stability of electron-exact clathrates and affects their rattler behavior. Targeted reactive synthesis from elemental precursors is attempted, resulting in two novel ternary compounds. However, the targeted clathrate phases are not obtained. Further analysis reveals that the stability of ATPn clathrate compounds containing heavy elements, such as bismuth, depends strongly on spin-orbit effects, which are often neglected in high-throughput studies that compute formation energies. Finally, chemically induced superstructural ordering is described in relation to Wyckoff sites in the prototypical type-I clathrate unit cell.

cond-mat.mtrl-sci↗

arXiv2024

High Pressure Structural Behavior of Silicon Telluride (Si2Te3) Nanoplates

The high-pressure behavior of silicon telluride (Si2Te3), a two-dimensional (2D) layered material, was investigated using synchrotron X-ray powder diffraction in a diamond anvil cell to 11.5 GPa coupled with first-principles theory. Si2Te3 undergoes a phase transition at < 1 GPa from a trigonal to a hexagonal crystal structure. At higher pressures (> 8.5 GPa), X-ray diffraction showed the appearance of new peaks possibly coincident with a new phase transition, though we suspect Si2Te3 retains a hexagonal structure. Density functional theory calculations of the band structure reveal metallization above 9.1 GPa consistent with previous measurements of the Raman spectra and disappearance of color and transparency at pressure. The theoretical Raman spectra reproduce the prominent features of the experiment, though a deeper analysis suggests that the orientation of Si dimers dramatically influences the vibrational response. Given the complex structure of Si2Te3, simulation of the resulting high-pressure phase is complicated by disordered vacancies and the initial orientations of Si-Si dimers in the crushed layered phase.

cond-mat.mtrl-sci↗

arXiv2021

A systematic variational approach to band theory in a quantum computer

Quantum computers promise to revolutionize our ability to simulate molecules, and cloud-based hardware is becoming increasingly accessible to a wide body of researchers. Algorithms such as Quantum Phase Estimation and the Variational Quantum Eigensolver are being actively developed and demonstrated in small systems. However, extremely limited qubit count and low fidelity seriously limit useful applications, especially in the crystalline phase, where compact orbital bases are difficult to develop. To address this difficulty, we present a hybrid quantum-classical algorithm to solve the band structure of any periodic system described by an adequate tight-binding model. We showcase our algorithm by computing the band structure of a simple-cubic crystal with one $s$ and three $p$ orbitals per site (a simple model for Polonium) using simulators with increasingly realistic levels of noise and culminating with calculations on IBM quantum computers. Our results show that the algorithm is reliable in a low-noise device, functional with low precision on present-day noisy quantum computers, and displays a complexity that scales as $Ω(M^3)$ with the number $M$ of tight-binding orbitals per unit-cell, similarly to its classical counterparts. Our simulations offer a new insight into the ``quantum'' mindset and demonstrate how the algorithms under active development today can be optimized in special cases, such as band structure calculations.

quant-ph↗

arXiv2020

Discovery of Higher-Order Topological Insulators using the Spin Hall Conductivity as a Topology Signature

The discovery and realization of topological insulators, a phase of matter which hosts metallic boundary states when the $d$-dimension insulating bulk is confined to ($d-1$)-dimensions, led to several potential applications. Recently, it was shown that protected topological states can manifest in ($d-2$)-dimensions, such as hinge and corner states for three- and two-dimensional systems, respectively. These nontrivial materials are named higher-order topological insulators (HOTIs). Here we show a connection between spin Hall effect and HOTIs using a combination of {\it ab initio} calculations and tight-binding modeling. The model demonstrates how a non-zero bulk midgap spin Hall conductivity (SHC) emerges within the HOTI phase. Following this, we performed high-throughput density functional theory calculations to find unknown HOTIs, using the SHC as a criterion. We calculated the SHC of 693 insulators resulting in seven stable two-dimensional HOTIs. Our work guides novel experimental and theoretical advances towards higher-order topological insulators realization and applications.

cond-mat.mtrl-sci↗