Showing papers by "Davide Donadio published in 2016"
TL;DR: In this article, the authors assess the state of the art of nanophononics, describing the recent achievements and the open challenges in nanoscale heat transport, coherent phonon generation and exploitation, and in nano- and optomechanics.
Abstract: Understanding and controlling vibrations in condensed matter is emerging as an essential necessity both at fundamental level and for the development of a broad variety of technological applications. Intelligent design of the band structure and transport properties of phonons at the nanoscale and of their interactions with electrons and photons impact the efficiency of nanoelectronic systems and thermoelectric materials, permit the exploration of quantum phenomena with micro- and nanoscale resonators, and provide new tools for spectroscopy and imaging. In this colloquium we assess the state of the art of nanophononics, describing the recent achievements and the open challenges in nanoscale heat transport, coherent phonon generation and exploitation, and in nano- and optomechanics. We also underline the links among the diverse communities involved in the study of nanoscale phonons, pointing out the common goals and opportunities.
178 citations
TL;DR: Atomic simulations show that the metamaterials approach relying on localized resonances is very promising to engineer heat transport at the nanoscale, and establish a rationale between the size, shape, and period of the resonant structures, and the thermal conductivity of the nanowire.
Abstract: Understanding the design rules to obtain materials that enable a tight control of phonon transport over a broad range of frequencies would aid major developments in thermoelectric energy harvesting, heat management in microelectronics, and information and communication technology. Using atomistic simulations we show that the metamaterials approach relying on localized resonances is very promising to engineer heat transport at the nanoscale. Combining designed resonant structures to alloying can lead to extremely low thermal conductivity in silicon nanowires. The hybridization between resonant phonons and propagating modes greatly reduces the group velocities and the phonon mean free paths in the low frequency acoustic range below 4 THz. Concurrently, alloy scattering hinders the propagation of high frequency thermal phonons. Our calculations establish a rationale between the size, shape, and period of the resonant structures, and the thermal conductivity of the nanowire, and demonstrate that this approach is even effective to block phonon transport in wavelengths much longer than the size and period of the surface resonant structures. A further consequence of using resonant structures is that they are not expected to scatter electrons, which is beneficial for thermoelectric applications.
159 citations
TL;DR: Zeraati et al. as mentioned in this paper investigated the lattice thermal conductivity of newly proposed arsenene, the 2D honeycomb struc- ture of arsenic, using ab initio calculations.
Abstract: Highly Anisotropic Thermal Conductivity of Arsenene: an ab initio Study Majid Zeraati, 1 S. Mehdi Vaez Allaei, 1, 2, ∗ I. Abdolhosseini Sarsari, 3 Mahdi Pourfath, 4, 5 and Davide Donadio 6, 7, 8, 9, † Department of Physics, University of Tehran, Tehran 14395-547, Iran School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran School of Electrical and Computer Engineering, University of Tehran, Tehran 14395-515, Iran Institute for Microelectronics, TU Wien, Gushausstrase 27–29/E360, 1040 Vienna, Austria Department of Chemistry, University of California Davis, One Shields Ave. Davis, CA, 95616 Max Planck Institut f¨ ur Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany Donostia International Physics Center, Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastian, Spain IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain (Dated:) Elemental 2D materials exhibit intriguing heat transport and phononic properties. Here we have investigated the lattice thermal conductivity of newly proposed arsenene, the 2D honeycomb struc- ture of arsenic, using ab initio calculations. Solving the Boltzmann transport equation for phonons, we predict a highly anisotropic thermal conductivity, of 30.4 and 7.8 W/mK along the zigzag and armchair directions, respectively at room temperature. Our calculations reveal that phonons with mean free paths between 20 nm and 1 µm provide the main contribution to the large thermal con- ductivity in the zigzag direction, mean free paths of phonons contributing to heat transport in the armchair directions range between 20 and 100 nm. The obtained anisotropic thermal conductivity and feasibility of synthesis, in addition to high electron mobility reported elsewhere, make arsenene a promising material for nano-electronic applications and thermal management. I. INTRODUCTION The discovery of graphene as a stable atomically thin material has led to extensive investigation of similar 2D systems. Its properties such as high electron mobility 1 , and very high thermal conductivity 2–5 make graphene very appealing for applications in electronics, for packag- ing and thermal management 6–11 . The successful iso- lation of single-layer graphene fostered the search for further ultra-thin 2D structures, such as silicene, ger- manene, phosphorene, and transition metal dichalco- genides, e.g. MoS 2 and WS 2 12,13 . These materials are now considered for various practical usages due to their distinguished properties stemming from their low dimen- sionality. Thermal transport in 2D materials has recently attracted the attention of the scientific community, as anomalous heat conduction has been predicted to oc- cur in systems with reduced dimensionality 14 . Phononic properties and thermal conductivity vary significantly from one 2D system to another 5,15–18 . For example, sil- icene has a buckled structure and a much lower thermal conductivity 19,20 compared to graphene 12,21,22 . 2D structures of arsenic and phosphorous have been recently investigated 23–27 . Arsenic and phosphorus are in the 5th group of the periodic table and both have different allotropes. Black phosphorus is a layered al- lotrope of phosphorus similar to graphite, and the stabil- ity of its single layer form, named phosphorene has been probed both theoretically and experimentally 13,28 . Gray arsenic is one of the most stable allotropes of arsenic with a buckled layered structure 27,29 . In addition, arsenic has an orthorhombic phase (puckered) similar to black phosphorus 23,25,26 , and its monolayer is called arsenene (see Fig. 1). Experimental observations have shown that gray arsenic undergoes a structural phase transition to the orthorhombic precursor of arsenene at temperatures of about T = 370 K 30 . As a monolayer arsenene can have a direct band gap of the order of 1 eV, as opposed to the multilayer allotrope, which exhibits an indirect band gap 23,26 . According to our calculations, arsenene is stable as a puckered monolayer also near zero temper- ature, in agreement with previous reports 23,25,26 . Both phosphorene and arsenene exhibit diverse polymorphs, with electronic properties that vary from semiconduct- ing to semimetallic and metallic as a function of struc- ture and strain 23,27,31 . Low dimensionality and the versa- tility of their electronic structure make two-dimensional 5th group elemental systems very appealing, not only for fundamental studies, but also for practical applications in nano electronics. For the latter applications, it is how- ever essential to characterize thermal transport and heat dissipation, to predict their operating temperatures. In this Article we investigate heat conduction in ar- senene and we elucidate the anisotropy of its thermal con- ductivity. We consider “puckered” unstrained arsenene, which is a semiconductor 23 . Since in semiconductors phonons are the predominant heat carriers, we use first- principles anharmonic lattice dynamics calculations and the Boltzmann transport equation to compute phonon dispersion relations and thermal conductivity. Accord- ing to electronic structure calculations 23 , arsenene has a band gap of the order of 1 eV, thus we expect a negligible electronic contribution to κ, unless the system is doped or strained. For this reason we restrict our study to the phononic contribution to thermal transport.
114 citations
TL;DR: The molecular mechanism and the kinetics of ice formation on kaolinite, a clay mineral playing a key role in climate science, are unraveled and it is found that the formation of ice at strong supercooling in the presence of this clay is about 20 orders of magnitude faster than homogeneous freezing.
Abstract: Most ice in nature forms because of impurities which boost the exceedingly low nucleation rate of pure supercooled water. However, the microscopic details of ice nucleation on these substances remain largely unknown. Here, we have unraveled the molecular mechanism and the kinetics of ice formation on kaolinite, a clay mineral playing a key role in climate science. We find that the formation of ice at strong supercooling in the presence of this clay is about 20 orders of magnitude faster than homogeneous freezing. The critical nucleus is substantially smaller than that found for homogeneous nucleation and, in contrast to the predictions of classical nucleation theory (CNT), it has a strong two-dimensional character. Nonetheless, we show that CNT describes correctly the formation of ice at this complex interface. Kaolinite also promotes the exclusive nucleation of hexagonal ice, as opposed to homogeneous freezing where a mixture of cubic and hexagonal polytypes is observed.
87 citations
TL;DR: The Hamiltonian approach is the first to provide both energy conservation and the correct solvent structure everywhere in this system defined by two different MM potentials, which yields energy expressions that are many-body in nature.
Abstract: Adaptive quantum mechanical (QM)/molecular mechanical (MM) methods enable efficient molecular simulations of chemistry in solution. Reactive subregions are modeled with an accurate QM potential energy expression while the rest of the system is described in a more approximate manner (MM). As solvent molecules diffuse in and out of the reactive region, they are gradually included into (and excluded from) the QM expression. It would be desirable to model such a system with a single adaptive Hamiltonian, but thus far this has resulted in distorted structures at the boundary between the two regions. Solving this long outstanding problem will allow microcanonical adaptive QM/MM simulations that can be used to obtain vibrational spectra and dynamical properties. The difficulty lies in the complex QM potential energy expression, with a many-body expansion that contains higher order terms. Here, we outline a Hamiltonian adaptive multiscale scheme within the framework of many-body potentials. The adaptive expressio...
40 citations
TL;DR: This work derives a bottom-up, rigorous, Hamiltonian-based scheme that allows molecules to change from quantum to classical and vice versa on the fly as they diffuse through the system, both reducing overhead and making quantum grand-canonical simulations possible.
Abstract: Quantum delocalization of atomic nuclei affects the physical properties of many hydrogen-rich liquids and biological systems even at room temperature. In computer simulations, quantum nuclei can be modeled via the path-integral formulation of quantum statistical mechanics, which implies a substantial increase in computational overhead. By restricting the quantum description to a small spatial region, this cost can be significantly reduced. Herein, we derive a bottom-up, rigorous, Hamiltonian-based scheme that allows molecules to change from quantum to classical and vice versa on the fly as they diffuse through the system, both reducing overhead and making quantum grand-canonical simulations possible. The method is validated via simulations of low-temperature parahydrogen. Our adaptive resolution approach paves the way to efficient quantum simulations of biomolecules, membranes, and interfaces.
23 citations
TL;DR: The adsorption of phenol and phenoxy on the (111) surface of Au and Pt has been investigated by density functional theory calculations with the conventional PBE functional and three different non-local van der Waals exchange and correlation functionals and it is found that bothphenol andphenoxy on Au(111) are physisorbed.
Abstract: The adsorption of phenol and phenoxy on the (111) surface of Au and Pt has been investigated by density functional theory calculations with the conventional PBE functional and three different non-local van der Waals (vdW) exchange and correlation functionals. It is found that both phenol and phenoxy on Au(111) are physisorbed. In contrast, phenol on Pt(111) presents an adsorption energy profile with a stable chemisorption state and a weakly metastable physisorbed precursor. While the use of vdW functionals is essential to determine the correct binding energy of both chemisorption and physisorption states, the relative stability and existence of an energy barrier between them depend on the semi-local approximations in the functionals. The first dissociation mechanism of phenol, yielding phenoxy and atomic hydrogen, has been also investigated, and the reaction and activation energies of the resulting phenoxy on the flat surfaces of Au and Pt were discussed.
22 citations
TL;DR: This work proposes and validate the usage of a short-range modification of Coulomb potential, the Damped shifted force (DSF) model, in the context of the Hamiltonian adaptive resolution simulation (H-AdResS) scheme, and ensures a reliable reproduction of the structural and dynamical properties of the liquid.
Abstract: In adaptive resolution simulations the same system is concurrently modeled with different resolution in different subdomains of the simulation box, thereby enabling an accurate description in a small but relevant region, while the rest is treated with a computationally parsimonious model. In this framework, electrostatic interaction, whose accurate treatment is a crucial aspect in the realistic modeling of soft matter and biological systems, represents a particularly acute problem due to the intrinsic long-range nature of Coulomb potential. In the present work we propose and validate the usage of a short-range modification of Coulomb potential, the Damped shifted force (DSF) model, in the context of the Hamiltonian adaptive resolution simulation (H-AdResS) scheme. This approach, which is here validated on bulk water, ensures a reliable reproduction of the structural and dynamical properties of the liquid, and enables a seamless embedding in the H-AdResS framework. The resulting dual-resolution setup is implemented in the LAMMPS simulation package, and its customized version employed in the present work is made publicly available.
19 citations
TL;DR: This work uses the concept of hierarchical nano-grains to demonstrate thermal conductivity reduction in rocksalt lead chalcogenides and proposes a viable process to produce hierarchical thermoelectric materials by applying pressure via a mechanical load or a shockwave as a novel paradigm for material design.
Abstract: Thermoelectric materials are strategically valuable for sustainable development, as they allow for the generation of electrical energy from wasted heat. In recent years several strategies have demonstrated some efficiency in improving thermoelectric properties. Dopants affect carrier concentration, while thermal conductivity can be influenced by alloying and nanostructuring. Features at the nanoscale positively contribute to scattering phonons, however those with long mean free paths remain difficult to alter. Here we use the concept of hierarchical nano-grains to demonstrate thermal conductivity reduction in rocksalt lead chalcogenides. We demonstrate that grains can be obtained by taking advantage of the reconstructions along the phase transition path that connects the rocksalt structure to its high-pressure form. Since grain features naturally change as a function of size, they impact thermal conductivity over different length scales. To understand this effect we use a combination of advanced molecular dynamics techniques to engineer grains and to evaluate thermal conductivity in PbSe. By affecting grain morphologies only, i.e. at constant chemistry, two distinct effects emerge: the lattice thermal conductivity is significantly lowered with respect to the perfect crystal, and its temperature dependence is markedly suppressed. This is due to an increased scattering of low-frequency phonons by grain boundaries over different size scales. Along this line we propose a viable process to produce hierarchical thermoelectric materials by applying pressure via a mechanical load or a shockwave as a novel paradigm for material design.
17 citations
TL;DR: In this article, the authors utilized density functional theory and Boltzmann transport equation to compute the electronic properties of ultra-thin crystalline silicon membranes with thickness between 1 and 12 nm.
Abstract: Silicon nanostructures with reduced dimensionality, such as nanowires, membranes, and thin films, are promising thermoelectric materials, as they exhibit considerably reduced thermal conductivity. Here, we utilize density functional theory and Boltzmann transport equation to compute the electronic properties of ultra-thin crystalline silicon membranes with thickness between 1 and 12 nm. We predict that an optimal thickness of ∼7 nm maximizes the thermoelectric figure of merit of membranes with native oxide surface layers. Further thinning of the membranes, although attainable in experiments, reduces the electrical conductivity and worsens the thermoelectric efficiency.
14 citations
TL;DR: In this article, the authors use ab initio molecular dynamics simulations to unravel how specific molecular interactions occurring on calcium oxalate dihydrate surface can promote an anisotropic crystal growth.
Abstract: Understanding the molecular mechanisms which nature uses to control biomineral growth is a fundamental science goal with profound medical implication. In the case of calcium oxalate, a microscopic understanding of the interactions which regulate the growth and stabilization of metastable phases would permit to inhibit the growth of the crystals which are the main components of kidney stones. Here we use ab initio molecular dynamics simulations to unravel how specific molecular interactions occurring on calcium oxalate dihydrate surface can promote an anisotropic crystal growth. We find that the calcium oxalate dihydrate (100) and (101) surfaces are both hydrophilic and solvated by a strongly bound layer of water; however, they exhibit important differences in their ability to bind water and small molecules such as acetate. In particular, on the (100) surface, the more exposed Ca2+ ions can more strongly bind to negatively charged groups, exerting a protecting action on the surface and preventing its furth...
TL;DR: In this paper, the adsorption of iodobenzene molecules on the Pt(111) surface has been studied using density functional theory, and the dissociated structure of monoiodobenzenes was investigated.
TL;DR: In this article, the authors review the contribution of lattice dynamics and molecular dynamics simulation to understand nanoscale thermal transport in systems with reduced dimensionality, focusing on the effect of dimensionality in determining the phononic properties of carbon and semiconducting nanostructures, specifically considering the cases of carbon nanotubes, graphene and of silicon nanowires and ultra-thin membranes.
Abstract: The discovery of nanostructures and the development of growth and fabrication techniques of one- and two-dimensional materials provide the possibility to probe experimentally heat transport in low-dimensional systems. Nevertheless measuring the thermal conductivity of these systems is extremely challenging and subject to large uncertainties, thus hindering the chance for a direct comparison between experiments and statistical physics models. Atomistic simulations of realistic nanostructures provide the ideal bridge between abstract models and experiments. After briefly introducing the state of the art of heat transport measurement in nanostructures, and numerical techniques to simulate realistic systems at atomistic level, we review the contribution of lattice dynamics and molecular dynamics simulation to understanding nanoscale thermal transport in systems with reduced dimensionality. We focus on the effect of dimensionality in determining the phononic properties of carbon and semiconducting nanostructures, specifically considering the cases of carbon nanotubes, graphene and of silicon nanowires and ultra-thin membranes, underlying analogies and differences with abstract lattice models.