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Alfredo Pasquarello

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Related publications (226)

Metal adatoms on graphene and hexagonal boron nitride: Towards rational design of self-assembly templates

Periodically corrugated epitaxial graphene and hexagonal boron nitride (h-BN) on metallic substrates are considered as perspective templates for the self-assembly of nanoparticles arrays. By using first-principles calculations, we determine binding energie ...

2010

Alignment of defect levels and band edges through hybrid functionals: Effect of screening in the exchange term

Alfredo Pasquarello, Peter Broqvist, Hannu-Pekka Komsa

We investigate how various treatments of exact exchange affect defect charge transition levels and band edges in hybrid functional schemes for a variety of systems. We distinguish the effects of long-range vs short-range exchange and of local vs nonlocal e ...

2010

Dangling bond charge transition levels in AlAs, GaAs, and InAs

Alfredo Pasquarello, Hannu-Pekka Komsa

Charge transition levels of dangling bonds in III-V semiconductors (AlAs, GaAs, and InAs) are determined via hybrid density-functional calculations. In GaAs, the Ga and As levels are found at 0.28 eV below the conduction band and at 0.16 eV above the valen ...

2010

Electron trapping in substoichiometric germanium oxide

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Model structures of substoichiometric germanium oxide generated by ab initio molecular dynamics reveal a rich variety of bonding configurations, including threefold coordinated Ge and O atoms which correspond to valence alternation pairs. A sizable fractio ...

American Institute of Physics2010

Defect levels of the Ge dangling bond defect

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

Defect levels of dangling bonds in germanium are calculated through the use of hybrid density functionals. The theoretical approach is first validated through the consideration of the well-characterized defect levels of the dangling bond in silicon, for wh ...

2010

Structural assignments of NMR chemical shifts in GexSe1-x glasses via first-principles calculations for GeSe2, Ge4Se9, and GeSe crystals

Carlo Massobrio, Alfredo Pasquarello, Mikhail Kibalchenko

Structural assignments are determined for Se-77 and Ge-73 chemical shifts through density-functional NMR calculations for GeSe2, Ge4Se9, and GeSe crystals. In particular, a very good agreement between calculated and measured Se-77 isotropic chemical shifts ...

2010

Energy levels of candidate defects at interfaces SiC/SiO2 interfaces

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

We determine energy levels of candidate defects for the high defect density observed just below the SiC conduction band at SiC/SiO 2 interfaces. We address C interstitials and H bridge defects which both show defect levels in the upper part of the SiC band ...

2010

Atomistic model structure of the Ge(100)-GeO2 interface

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

An atomistic model of the Ge-GeO2 interface has been generated through first-principle methods based on density functional theory. The interface model consists of amorphous GeO2 connected to crystalline Ge through a substoichiometric oxide region showing r ...

2009

Band offsets at the Ge/GeO2 interface through hybrid density functionals

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Band offsets of the Ge/GeO2 interface are calculated through a hybrid density functional scheme. We first generate a model of disordered GeO2 through ab initio molecular dynamics to describe the oxide component. For addressing the interface, we then consid ...

AIP American Institute of Physics2009

Li-related defects in ZnO : hybrid functional calculations

Nava Setter, Alexander Tagantsev, Alfredo Pasquarello, Audrius Alkauskas, Alexandra Sarabando de Carvalho

Hybrid density functional calculations are used to model substitutional lithium (LiZn) and interstitial lithium (Lii) defects in ZnO. The calculated transition levels and formation energies are compared to those obtained using a semilocal density functiona ...

2009

Atomic structure of the two intermediate phase glasses SiSe4 and GeSe4

Alfredo Pasquarello

The microscopic origin of the intermediate phase in two prototypical covalently bonded A(x)B(1-x) network glass forming systems, where A=Ge or Si, B=Se, and 0

2009

First principles investigation of defect energy levels at semiconductor-oxide interfaces: Oxygen vacancies and hydrogen interstitials in the Si-SiO2-HfO2 stack

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

We introduce a scheme for the calculation of band offsets and defect energy levels at semiconductor-oxide interfaces. Our scheme is based on the use of realistic atomistic models of the interface structure and of hybrid functionals for the evaluation of th ...

American Institute of Physics2009

First principles study of substoichiometric germanium oxides

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Using density functional calculations, we studied substoichiometric Ge oxides through a series of crystalline models representing the various oxidation states. We evaluated deviations with respect to a bond-energy description in terms of penalty energies f ...

2009

QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials

Roberto Car, Alfredo Pasquarello, Gabriele Sclauzero, Nicola Marzari, Lorenzo Paulatto, Matteo Cococcioni

QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). The ac ...

2009

Hybrid-functional calculations with plane-wave basis sets: Effect of singularity correction on total energies, energy eigenvalues, and defect energy levels

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

When described through a plane-wave basis set, the inclusion of exact nonlocal exchange in hybrid functionals gives rise to a singularity, which slows down the convergence with the density of sampled k points in reciprocal space. In this work, we investiga ...

2009

Medium-range structure of vitreous SiO2 obtained through first-principles investigation of vibrational spectra

Alfredo Pasquarello, Paolo Umari, Luigi Giacomazzi

Using a density-functional framework, we investigate the vibrational spectra of vitreous SiO2 to determine to what extent these spectra provide information about the medium-range structure of the oxide network. We carry out a comparative study involving th ...

2009

A hybrid density functional study of lithium in ZnO: Stability, ionization levels, and diffusion

Nava Setter, Alexander Tagantsev, Alfredo Pasquarello, Audrius Alkauskas, Alexandra Sarabando de Carvalho

The properties of interstitial and substitutional Li in wurtzite ZnO are modeled using hybrid density functional calculations. We investigate the impact of the band-gap error on the formation energies of the two defects and their dependence on the Fermi le ...

2009

Nitrogen fixation at passivated Fe nanoclusters supported by an oxide surface: Identification of viable reaction routes using density functional calculations

Harald Brune, Alfredo Pasquarello, Zeljko Sljivancanin

Using density-functional calculations, we investigate the possibility of ammonia synthesis at supported Fe nanoclusters along catalytic routes closely resembling those in biological nitrogen fixation. To achieve similar catalytic conditions as at the activ ...

2009

Magnetoresistive junctions based on epitaxial graphene and hexagonal boron nitride

Alfredo Pasquarello, Oleg Yazyev

We propose monolayer epitaxial graphene and hexagonal boron nitride (h-BN) as ultimate thickness covalent spacers for magnetoresistive junctions. Using a first-principles approach, we investigate the structural, magnetic, and spin transport properties of s ...

2009

Effect of metal elements in catalytic growth of carbon nanotubes

Alfredo Pasquarello, Oleg Yazyev

Using first-principles calculations, we model the chemical vapor deposition (CVD) growth of carbon nanotubes (CNT) on nanoparticles of late-transition (Ni, Pd, Pt) and coinage (Cu, Ag, Au) metals. The process is analyzed in terms of the binding of mono- an ...

2008

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