Density functional theory method for non-equilibrium charge transport calculations: TRANSAMPA

Novaes, Frederico D.; Silva, Antônio José Roque da; Fazzio, A.

doi:10.1590/s0103-97332006000500039

Cited by 60 publications

(57 citation statements)

References 40 publications

(55 reference statements)

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“…Note that any treatment for the contribution to the charge density has not been clarified in the other implementations. 17,18,19,20,21,22,23 Thus, we carefully calculate the charge density in the central region by considering three contributions:…”

Section: Charge Density Near the Boundarymentioning

confidence: 99%

“…3,4,6 (ii) the electronic structure of the scattering region under a finite source-drain bias voltage is self-consistently determined by combining with first principle electronic structure calculation methods such as the density functional theory (DFT) and the Hartree-Fock (HF) method. 17,18,19,20,21,22,23,24,25,26,27 (iii) many body effects in the transport properties, e.g., electron-phonon 28,29,30,31,32,33 and electron-electron interactions, 34,35,36,37 might be included through selfenergies without largely deviating the theoretical framework. (iv) its applicability to large-scale systems can be anticipated, since the NEGF method relies practically on the locality of basis functions in real space, resulting in computations for sparse matrices.…”

Section: Introductionmentioning

confidence: 99%

“…15 Due to those potential advantages, recently several groups have implemented the NEGF method coupled with the DFT or HF method using atomic-type or the other local basis functions with successful applications for calculations of the electronic transport properties. 15,16,17,18,19,20,21,22,23,24,25,26,27 However, a highly accurate and efficient implementation method must be still developed from the following two reasons: The first obvious reason is to extend the applicability of the NEGF method to large-scale systems. The efficient implementation might lead to more challenging applications of the NEGF method to very largescale complicated systems.…”

Section: Introductionmentioning

confidence: 99%

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Efficient implementation of the nonequilibrium Green function method for electronic transport calculations

2010

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An efficient implementation of the nonequilibrium Green function (NEGF) method combined with the density functional theory (DFT) using localized pseudo-atomic orbitals (PAOs) is presented for electronic transport calculations of a system connected with two leads under a finite bias voltage. In the implementation, accurate and efficient methods are developed especially for evaluation of the density matrix and treatment of boundaries between the scattering region and the leads. Equilibrium and nonequilibrium contributions in the density matrix are evaluated with very high precision by a contour integration with a continued fraction representation of the Fermi-Dirac function and by a simple quadrature on the real axis with a small imaginary part, respectively. The Hartree potential is computed efficiently by a combination of the two dimensional fast Fourier transform (FFT) and a finite difference method, and the charge density near the boundaries is constructed with a careful treatment to avoid the spurious scattering at the boundaries. The efficiency of the implementation is demonstrated by rapid convergence properties of the density matrix. In addition, as an illustration, our method is applied for zigzag graphene nanoribbons, a Fe/MgO/Fe tunneling junction, and a LaMnO3/SrMnO3 superlattice, demonstrating its applicability to a wide variety of systems.

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Section: Charge Density Near the Boundarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Efficient implementation of the nonequilibrium Green function method for electronic transport calculations

2010

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“…For our transport calculations we use a combination of DFT and the Non-Equilibrium Green's Function Formalism (NEGF). [35][36][37][38] In order to perform those calculations, the system is divided into three parts, namely, a central scattering corresponding to the 4ND defect -with or without the CO -and two (left-and right-hand side) electrodes as shown in Fig. 1(a).…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Ab-initio calculations for a realistic sensor: A study of CO sensors based on nitrogen-rich carbon nanotubes

et al. 2012

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The use of nanoscale low-dimensional systems could boost the sensitivity of gas sensors. In this work we simulate a nanoscopic sensor based on carbon nanotubes with a large number of binding sites using ab initio density functional electronic structure calculations coupled to the Non-Equilibrium Green's Function formalism. We present a recipe where the adsorption process is studied followed by conductance calculations of a single defect system and of more realistic disordered system considering different coverages of molecules as one would expect experimentally. We found that the sensitivity of the disordered system is enhanced by a factor of 5 when compared to the single defect one. Finally, our results from the atomistic electronic transport are used as input to a simple model that connects them to experimental parameters such as temperature and partial gas pressure, providing a procedure for simulating a realistic nanoscopic gas sensor. Using this methodology we show that nitrogen-rich carbon nanotubes could work at room temperature with extremely high sensitivity

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“…In addition to the experimental work in this area, intense effort has gone into the development of efficient computational methods. Those proposed so far fall into two broad classes: methods investigating the evolution of electronic charge density in a system perturbed by a timedependent potential [1][2][3][4][5][6], and methods calculating the current balance in a steady-state system [1,[7][8][9][10][11][12][13][14][15][16][17]. The latter are conceptually simpler and computationally much less demanding than the former.…”

Section: Introductionmentioning

confidence: 99%

Spin-dependent electronic conduction along zigzag graphene nanoribbons bearing adsorbed Ni and Fe nanostructures

García‐Fuente¹,

Gallego²,

Vega³

2014

J. Phys.: Condens. Matter

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Using SMEAGOL, an ab initio computational method that combines the non-equilibrium Green's function formalism with density-functional theory, we calculated spin-specific electronic conduction in systems consisting of single Fe n and Ni n nanostructures (n = 1−4) adsorbed on a hydrogen-passivated zigzag graphene nanoribbon. For each cluster we considered both ferromagnetically and antiferromagnetically coupled ribbon edges (Ferro-F and Ferro-A systems, respectively). Adstructures located laterally on Ferro-A ribbons caused significant transmittance loss at energies 0.6-0.25 eV below the Fermi level for one spin and 0.2-0.4 eV above the Fermi level for the other, allowing the potential use of these systems in transistors to create a moderately spin-polarized current of one or the other sign depending on the gate voltage. Ni 3 and Ni 4 clusters located at the centre of Ferro-F ribbons exhibited a strong spin-filtering effect in a narrow energy window around the Fermi level.

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Density functional theory method for non-equilibrium charge transport calculations: TRANSAMPA

Cited by 60 publications

References 40 publications

Efficient implementation of the nonequilibrium Green function method for electronic transport calculations

Efficient implementation of the nonequilibrium Green function method for electronic transport calculations

Ab-initio calculations for a realistic sensor: A study of CO sensors based on nitrogen-rich carbon nanotubes

Spin-dependent electronic conduction along zigzag graphene nanoribbons bearing adsorbed Ni and Fe nanostructures

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