E. Z. da Silva

Universidade Estadual de Campinas (UNICAMP)

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Miguel A. San‐Miguel

Universidade Estadual de Campinas (UNICAMP)

E. Longo

Universidade Federal de São Carlos

A. Fazzio

Universidade Federal do ABC

Antônio J. R. da Silva

Brazilian Center for Research in Energy and Materials

Juán Andrés

Universitat Jaume I

Frederico D. Novaes

Institut de Ciència de Materials de Barcelona

Giovani M. Faccin

Universidade Federal da Grande Dourados

Edgard P. M. Amorim

Universidade do Estado de Santa Catarina

Zenner S. Pereira

Universidade Federal Rural do Semi-Árido

L. Cabral

Universidade Estadual de Campinas (UNICAMP)

Cooperative Institutions

Universidade Federal de São Carlos

Universidade Estadual de Campinas (UNICAMP)

Universidade de São Paulo

Universidade Estadual Paulista (Unesp)

Universitat Jaume I

Centro Universitário de Araraquara

Brazilian Center for Research in Energy and Materials

Universidade Federal de Minas Gerais

Centro de Desenvolvimento da Tecnologia Nuclear

Universitat de València

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Order and disorder in iron-titanium

Physical review. B, Condensed matter (1987)

E. Z. da Silva P. Strange W. M. Temmerman B. L. Györffy

We have studied the electronic structure of the ordered intermetallic compound Ti-Fe with CsCl structure and a corresponding hypothetical random solid solution on a bcc and CsCl lattice using comparable first-principles self-consistent calculations. The differences of the one-electron spectra enable us to comment on the nature of bonding and the absence of disorder in this interesting system.

Lattice (music)

10.1103/physrevb.36.3015

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Citations (16)

In situgrowth of Ag nanoparticles onα-Ag₂WO₄under electron irradiation: probing the physical principles

Nanotechnology (2016)

Miguel A. San‐Miguel E. Z. da Silva Sônia M. Zanetti M. Cilense Maria Tereza Fabbro

Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements.

Characterization

Electron beam processing

Nanomaterials

10.1088/0957-4484/27/22/225703

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Citations (35)

The Role of Simulations in Nanoscience, a Case Study: Gold Nanowires

Diffusion and defect data, solid state data. Part B, Solid state phenomena/Solid state phenomena (2007)

E. Z. da Silva

10.4028/3-908451-30-2.1007

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Helical [110] Gold Nanowires Make Longer Linear Atomic Chains

Physical Review Letters (2008)

Edgard P. M. Amorim E. Z. da Silva

Quantum mechanical molecular dynamics shows that gold nanowires formed along the [110] direction reconstruct upon stress to form helical nanowires. The mechanism for this formation is discussed. These helical nanowires evolve on stretching to form linear atomic chains. Because helical nanowires do not form symmetrical tips, a requirement to stop the growth of atomic chains, these nanowires produce longer atomic chains than other nanowires. These results are obtained resorting to the use of tight-binding molecular dynamics and ab initio electronic structure calculations.

Quantum wire

10.1103/physrevlett.101.125502

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Citations (23)

Nanociência: a próxima grande idéia?

Revista USP (2008)

E. Z. da Silva

10.11606/issn.2316-9036.v0i76p78-87

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Citations (2)

Estudo de adsorção de impurezas moleculares e caminhos de reação em nanofios de ouro

Ana Paula Fávaro Nascimento E. Z. da Silva

A fabricacao e o estudo de nanofios de ouro despertam grande interesse na comunidade cientifica, na tentativa de maior entendimento de efeitos quânticos de sistemas em escala reduzida, assim como na possibilidade de seu uso em aplicacoes tecnologicas. Uma vez que os nanofios de ouro apresentam propriedades surpreendentes quando dopados por impurezas atomicas fomos motivados a estudar como estas se formam. Devido ao fato de em escala nanoscopica o ouro apresentar atividade catalitica, consideramos que a presenca de impurezas se deve a reacao de pequenas moleculas em nanofios de Au. O estudo foi realizado por meio de calculos abinitio via Teoria do Funcional da Densidade, usando o codigo computacional SIESTA. A metodologia para o estudo da estrutura eletronica desses sistemas foi a de otimizacao de geometria e de dinâmica molecular ab initio. Nosso foco de estudo foi encontrar caminhos reacionais para a formacao de impurezas atomicas de carbono ou de oxigenio nas cadeias atomicas lineares de nanofios monoatomicos. A analise se baseou na interacao entre duas moleculas catalisada pelo nanofio, as moleculas consideradas em nosso estudo foram CO e O2. Um estudo extensivo e detalhado das possiveis reacoes foi feito. Dentre os varios caminhos estudados, uma reacao sequencial onde uma molecula de O2 e adsorvida por apenas um dos seus oxigenios, inicia um processo, que seguido pela adsorcao de uma molecula de CO, leva a formacao de um complexo O2-CO ligado a cadeia atomica do nanofio. Nos mostramos situacoes onde este complexo fica ativado e reage formando uma molecula de CO2 que vai para a fase gasosa deixando o nanofio dopado com um atomo de oxigenio. Portanto este trabalho apresenta um caminho reacional para a formacao de uma impureza atomica na cadeia atomica de um nanofio de ouro, uma questao que esperava uma solucao a quase uma decada Abstract

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Martensitic transformation of Cu on Ag(001) and Cu on Au(001) studied with classical molecular dynamics

Physical Review B (2009)

Zenner S. Pereira E. Z. da Silva

The growth of Cu thin films on Ag(001) and Au(001) substrates was modeled using molecular dynamics with classical potentials. We observed that deposited atoms formed an unstable bcc or bcc/body-centered-tetragonal structure, in agreement with previous experiments. We show that the formation of such structures is related to film thickness and temperature that was analyzed in the interval from 200 to 600 K. bcc nucleation was measured by observing the relation between thickness and temperature of the deposited thin film. The martensitic transformation accompanied by a stripe pattern occurred as a consequence of the distortions caused by the underlying substrate lattice. The stripe patterns were measured as 57 and $61\text{ }\text{\AA{}}$ for Cu on Ag and Cu on Au, respectively. Monolayer spacing and coordination number of atoms were calculated, clearly evidencing the formed structures. Local structures were studied using the Ackland-Jones method, to determine the phases of the deposited films.

Tetragonal crystal system

Diffusionless transformation

Lattice (music)

10.1103/physrevb.79.115404

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Citations (6)

Computational Modeling for the Ag Nanoparticle Coalescence Process: A Case of Surface Plasmon Resonance

The Journal of Physical Chemistry C (2017)

Giovani M. Faccin Miguel A. San‐Miguel Juán Andrés E. Longo E. Z. da Silva

Motivated by recent transmission electron microscopy (TEM) experiments on α-Ag2WO4, the coalescence process of Ag nanoparticles (NPs) is investigated using molecular dynamics (MD) simulations. These Ag NPs are formed by irradiation of α-Ag2WO4 crystals by electrons from a TEM gun. This behavior can be considered as a clear example of surface plasmon resonance (SPR), in which Ag NP coalescence processes are controlled by dipole–dipole interaction forming larger clusters. The interactions between Ag NPs along the coalescence processes are studied using MD simulations with embedded atom method (EAM) effective potentials for Ag. With these choices of methods, coalescence is studied by addressing different scenarios for the interacting NPs, which all could possibly occur in experiments.

Coalescence (physics)

10.1021/acs.jpcc.7b00769

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Citations (19)

Effects of the confining interaction on mesoscopic superconducting cylinders

Physica status solidi. C, Conferences and critical reviews/Physica status solidi. C, Current topics in solid state physics (2007)

A. Pasaje José M. Alcaraz Calero J. C. Granada E. Z. da Silva

Abstract The most important feature of a mesoscopic superconductor is that its shape and size have an important effect on the interplay of the magnetic field and superconducting condensate. Usually this effect is investigated via the Ginzburg‐Landau (GL) equations, solved together with the conventional boundary condition. This condition implies that the normal component of the superconducting current is equal to zero. However, the approach based on the GL functional for the free energy does not include the contribution acquired by the cooper pairs due to the confining interaction. In this work we use a generalized GL theory proposed by Shanenko and Ivanov, including the confining interaction, in order to study the way the terms arising from the confining potential affect the critical behavior in mesoscopic superconducting samples with cylindrical symmetry without an applied magnetic field. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Mesoscopic physics

Cooper pair

Ginzburg–Landau theory

Energy functional

10.1002/pssc.200675928

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Disentangling the Effects of Laser and Electron Irradiation on AgX (X = Cl, Br, and I): Insights from Quantum Chemical Calculations

Nano Letters (2024)

L. Cabral Edson R. Leite E. Longo Miguel A. San‐Miguel E. Z. da Silva

The effects on the lattice structure and electronic properties of different polymorphs of silver halide, AgX (X = Cl, Br, and I), induced by laser irradiation (LI) and electron irradiation (EI) are investigated using a first-principles approach, based on the electronic temperature (Te) within a two-temperature model (TTM) and by increasing the total number of electrons (Ne), respectively. Ab initio molecular dynamics (AIMD) simulations provide a clear visualization of how Te and Ne induce a structural and electronic transformation process during LI/EI. Our results reveal the diffusion processes of Ag and X ions, the amorphization of the AgX lattices, and a straightforward interpretation of the time evolution for the formation of Ag and X nanoclusters under high values of Te and Ne. Overall, the present work provides fine details of the underlying mechanism of LI/EI and promises to be a powerful toolbox for further cross-scale modeling of other semiconductors.

Nanoclusters

10.1021/acs.nanolett.3c04130

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Citations (1)