New paper accepted in Physical Review B – Thermal conductivity decomposition in two-dimensional materials: Application to graphene

Our second paper of 2017 “Thermal conductivity decomposition in two-dimensional materials: Application to graphene” has just been accepted for publication in Physical Review B.

In this work we propose a decomposition of the microscopic heat current in atomistic molecular dynamics simulations into in-plane and out-of-plane components, corresponding to the in-plane and out-of-plane phonon dynamics, respectively. This decomposition allows a direct computation of the corresponding thermal conductivity components in two-dimensional materials. We apply this decomposition to study heat transport in suspended graphene, using both equilibrium and non-equilibrium molecular dynamics simulations. We show that the flexural component is responsible for about two thirds of the total thermal conductivity in unstrained graphene, and the acoustic flexural component is responsible for the logarithmic divergence of the conductivity when a sufficiently large tensile strain is applied, in accordance with my PRB Editors’ Suggestion paper with Prof. Davide Donadio in 2013.

The manuscript is a product of our ongoing collaboration with Dr. Zheyong Fan and Dr. Ari Harju at Aalto University, and a follow-up to our PRB paper in 2015.

The paper is available here.  A preprint version is available here.

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New paper in The Journal of Physical Chemistry C – Atomic Adsorption on Nitrogenated Holey Graphene

Our first paper of 2017 “Atomic Adsorption on Nitrogenated Holey Graphene” has just been accepted for publication in The Journal of Physical Chemistry C.

In this work we employ first principles calculations and a hybrid Quantum Mechanics:Molecular Mechanics method (ONIOM) to investigate the adsorption of H, B, and O on nitrogenated holey graphene (NHG). It is a novel 2D material with C2N stoichiometry which has been recently synthesized in the group of Prof. Jong-Beom Baek at the Ulsan National Institute of Science and Technology in Korea. We find that H and B prefer to adsorb on top of a nitrogen atom, while O prefers to adsorb on top of a carbon-carbon bond. We show that the electronic structure of NHG changes due to the presence of adatoms, with the appearance of midgap states, close to the Fermi level. In the case of NHG+H and NHG+B we observe the appearance of a finite magnetic moment, related to the midgap states, which could give rise to a magnetoresistance effect.

The manuscript is a product of my first postdoc supervision, developed by Dr. Raphael M. Tromer at UFRN since early 2016. It also includes collaboration with Prof. M.G.E. da Luz (UFPR) and Prof. Mauro S. Ferreira (Trinity College Dublin). Computational resources for this project were provided by the High Performance Computing Center (NPAD) at UFRN and Laboratorio Central de Processamento de Alto Desempenho (LCPAD) at UFPR.

This is another chemistry first for me: it is my first paper as senior author in a physical chemistry journal. Can I call myself a chemical physicist now? Really?

The paper is available here.  Direct link to PDF here.

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School and Workshop: Thermal and Electronic Transport in Nanostructures

Today we kick-off our event Thermal and Electronic Transport in Nanostructures, which takes place at the International Institute of Physics – Universidade Federal do Rio Grande do Norte from 31/10/2016 to 11/11/2016. It is a two-week event focusing on the conduction of heat and electricity in the nanoscale. The event includes a series of lectures aimed at students and several scientific talks. We have around 60 participants from three continents and more than 12 different countries.

The idea for this workshop came from a post-seminar discussion with visiting Prof. Giulio Casati, back in 2014. We submitted the proposal to the international advisory board of the IIP early 2015, when it was approved. Since than we had full support from the IIP staff, who guided us through all the bureaucracy, including the request of additional funds from the Brazilian government. We are grateful for the financial support provided by CAPES to this event.

I hope the participants will enjoy this event as much as we enjoyed organizing the whole thing.

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TNG @ XXXIX National Meeting on Condensed Matter Physics

The XXXIX National Meeting on Condensed Matter Physics promoted by the Brazilian Physical Society takes place in Natal, Rio Grande do Norte, from 3 to 7 of September.

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Several group members will present our latest results during the meeting.

Posters (15:30 – 17:00) – 5 Sep 2016
MATERIALS BEYOND GRAPHENE AND VAN DER WAALS HETEROSTRUCTURES

P087 Thermal conductivity of nitrogenated holey graphene under strain
Louis G. C. S. Sá, Bohayra Mortazavi, Luiz Felipe C. Pereira

P088 Thermal transport in graphene-BN superlattices
Isaac de Macêdo Félix, Luiz Felipe C. Pereira

P091 Atomic adsorption on nitrogenated holey graphene
Raphael M. Tromer, Mauro S. Ferreira, Luiz Felipe C. Pereira

Symposia I (8:30 – 10:00) – 6 Sep 2016
CURRENT TOPICS IN GRAPHENE AND BEYOND III

09:30 Amorphized graphene: A stiff material with low thermal conductivity
Bohayra Mortazavi, Timon Rabczuk, Zheyong Fan, Luiz Felipe C. Pereira, Ari Harju

 

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Experimental techniques and physics in 2D materials

I have been invited to give a presentation on our work on thermal transport in nanostructures at Universidad de Los Andes in Bogotá. The event “Experimental techniques and physics in 2D materials” takes place on 28 and 29 July, and it is aimed at graduate students in Colombia and Latin America.facebook_1469584193550

It was an excellent meeting and a great opportunity to see some of the amazing work done in 2D materials.

Thanks to Prof. Yenny Hernandez from Universidad de Los Andes and Prof. Jairo Velasco from University of California Santa Cruz for organising this great event and for the invitation.

 

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Our work was featured on the cover of the Journal of Applied Physics.

Our paper “Controlling resonant tunneling in graphene via Fermi velocity engineering” has been featured on the cover of the Journal of Applied Physics Volume 119 Number 24, dated 28 June 2016. Figure 2 of our article was chosen for the cover of this issue.

We are very excited since this is the first time we get on the cover of a publication. Great fun!

Coverage from UFRN news.

Coverage from UFRPE news.

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New paper in RSC Advances – Anisotropic thermal conductivity and mechanical properties of phagraphene: A molecular dynamics study

Our latest paper “Anisotropic thermal conductivity and mechanical properties of phagraphene: A molecular dynamics study” has been accepted for publication in RSC Advances.

In this work we calculate thermal conductivity, phonon mean free path, elastic modulus and mechanical strength of a novel 2D carbon allotrope named phagraphene, which contains pentagonal, hexagonal and heptagonal carbon rings. We show that the thermal conductivity of phagraphene is anisotropic and one order of magnitude smaller than that of graphene, but its elastic modulus is only about 15% smaller.

It is another product of our fruitful collaboration with Dr. Bohayra Mortazavi and Prof. Timon Rabczuk of Bauhaus-Universität Weimar.

This is also my first paper as first author in a chemistry journal. Can I call myself a chemical physicist now?

The paper is available here.

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New paper accepted in the Journal of Applied Physics – Controlling resonant tunneling in graphene via Fermi velocity engineering

Our latest paper “Controlling resonant tunneling in graphene via Fermi velocity engineering” has been accepted for publication in the Journal of Applied Physics.

In this work we show that it is possible to control the electronic transmission along a graphene sample with a periodic modulation in its Fermi velocity.

It has been done in collaboration with my colleague Prof. Claudionor G. Bezerra and his former postdoc, now a faculty member at Universidade Federal Rural de Pernambuco, Prof. Jonas R. F. Lima.

This is my first paper in the Journal of Applied Physics since 2010. It sure is nice to be back.

The paper is available here.

UPDATE: This paper has been featured on the cover of Volume 119 Number 24 of the Journal of Applied Physics.

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Another paper accepted in Carbon – Thermal conductivity and mechanical properties of nitrogenated holey graphene

Our latest paper “Thermal Conductivity and Mechanical Properties of Nitrogenated Holey Graphene”  has been accepted for publication in Carbon.

In this work we calculate thermal conductivity, elastic modulus and mechanical strength of a novel graphene-derived material named nitrogenated holey graphene.

This is my first paper as senior author, and I am very proud of it.

It is also another product of our collaboration with Dr. Bohayra Mortazavi of Bauhaus-Universität Weimar.

The paper is available here.

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Master’s Thesis Defense: Isaac de Macedo Felix

Our first graduate student, Mr. Isaac de Macedo Felix, will present his Master’s thesis on Tuesday (29.03.2016) at 10:30 am, in the auditorium of the Physics Department (DFTE).

The thesis, entitled “Thermal transport in graphene-hBN superlattice nanoribbons”, employed non-equilibrium molecular dynamics simulations to calculate the thermal conductivity of hybrid graphene-hBN nanoribbons.

Everybody is welcome to the public defense.

UPDATE: Isaac has passed his defense with flying colours. He will now pursue his doctorate in our group. Congratulations!

Prof. Claudionor Bezerra, Prof. Luiz Felipe Pereira, Isaac Felix, Prof. Anderson Barbosa

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