Publicaciones: Modelización y Simulación

Hello world! Please change me in Site Preferences -> This Category/Section -> Lower Description Bar

13

Jun 2018

Effects of acceptor doping on a metalorganic switch: DFT vs. model analysis

Posted by / in Publicaciones Destacadas, Publicaciones: Modelización y Simulación, Publications 2018, Publications Modelling 2018, Últimas Publicaciones CINN / No comments yet

We propose a molecular switch based on copper dioxolene molecules with valence tautomeric properties. We study the system using density functional theory and a model Hamiltonian that can properly account for electronic correlations in these complex molecular systems. We compute the transport properties of the junction with a Cu–dioxolene unit sandwiched between gold electrodes and analyze its dependence on the valence tautomeric state of the molecule. We also study the effects of doping with ICl2 acceptor molecules on the magnetic and electronic features of the device. We find that in the absence of dopants, the Cu–dioxolene unit is weakly charged in a S = 1/2 spin state. However, the acceptors increase the charge state of the molecule and make possible a transition between the high-spin (S = 1) triplet and the low-spin (S = 0) singlet. The IVdependence shows a manifestation of spin filtering and a voltage-induced multistable behavior that can have several applications in nanoscale electronic devices.

Please select the social network you want to share this page with:

25

May 2018

Spin-state dependent conductance switching in single molecule-graphene junctions

Posted by / in Publicaciones Destacadas, Publicaciones: Modelización y Simulación, Publications 2018, Publications Modelling 2018, Últimas Publicaciones CINN / No comments yet

Spin-crossover (SCO) molecules are versatile magnetic switches with applications in molecular electronics and spintronics. Downscaling devices to the single-molecule level remains, however, a challenging task since the switching mechanism in bulk is mediated by cooperative intermolecular interactions. Here, we report on electron transport through individual Fe-SCO molecules coupled to few-layer graphene electrodes via π–π stacking. We observe a distinct bistability in the conductance of the molecule and a careful comparison with density functional theory (DFT) calculations allows to associate the bistability with a SCO-induced orbital reconfiguration of the molecule. We find long spin-state lifetimes that are caused by the specific coordination of the magnetic core and the absence of intermolecular interactions according to our calculations. In contrast with bulk samples, the SCO transition is not triggered by temperature but induced by small perturbations in the molecule at any temperature. We propose plausible mechanisms that could trigger the SCO at the single-molecule level.

Please select the social network you want to share this page with:

11

Dec 2017

Localized double phonon scattering and DOS induced thermoelectric enhancement of degenerate nonstoichiometric Li1-xNbO2 compounds

Posted by / in Publicaciones 2017, Publicaciones Modelización & Simulación 2017, Publicaciones: Modelización y Simulación, Últimas Publicaciones CINN / No comments yet

We report the synthesis and thermoelectric properties of a new p-type oxide thermoelectric material (Li1-xNbO2, with x ¼ 0–0.6), in which Li-vacancies play a significant role in the enhancement of the thermoelectric performance. The electrical conductivity drastically increases due to Li-vacancies, resulting in an increase in the hole carrier concentration. A remarkable enhancement in the power factor is observed, which is comparable to well-known oxide thermoelectrics. The carrier concentration was not significantly dependent on the temperature, while the Hall mobility shows negative temperaturedependence. The Seebeck coefficient is linearly proportional to temperature, and the density of the state effective mass ðm* dÞ was estimated by using the Pisarenko relation. The thermal conductivity was substantially reduced by Li-vacancies and Li-vacancy induced localized double phonon scattering. Density functional theory (DFT) calculations reveal that the enhancement of the thermoelectric properties is mainly due to the increase in the electronic density of states (DOS) at the Fermi energy, which increases with hole concentration. All of the samples after high-temperature measurements are highly stable, which suggests that the well-synthesized nonstoichiometric Li1xNbO2 could be a new promising candidate material for high temperature thermoelectric applications.

Please select the social network you want to share this page with: