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We developed a density functional theory method to calculate electron current and magnetic fields in molecular films during dc transport. This approach efficiently models large graphene ribbons, revealing how adatoms affect conductivity and lattice structure.

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Area of Science:

  • Computational physics
  • Materials science
  • Condensed matter physics

Background:

  • Accurate simulation of electron transport in molecular films is crucial for understanding electronic devices.
  • Density functional theory (DFT) provides a framework for electronic structure calculations.
  • Modeling large systems and complex interactions, like lattice relaxation, remains computationally challenging.

Purpose of the Study:

  • To present a DFT-based formalism for calculating electron current density and induced magnetic fields in molecular films under dc transport.
  • To develop and apply efficient computational techniques for simulating electron transport in large graphene ribbons.
  • To investigate the influence of adatoms on the electronic properties and structural geometry of graphene.

Main Methods:

  • Utilizing density functional theory (DFT) for electronic structure calculations.
  • Developing a formalism to compute spatially continuous electron current density (j(r)) and induced magnetic fields (B(r)).
  • Employing scalable computational techniques suitable for systems of approximately 10^3 atoms, leveraging thousands of CPUs.

Main Results:

  • The formalism successfully calculates electron current density and induced magnetic fields in molecular films.
  • Simulations of electron transport in graphene ribbons show efficient scaling with computational resources.
  • Analysis of hydrogenated graphene reveals that adatoms impact the transmission function by introducing new states and inducing lattice relaxation.

Conclusions:

  • The presented DFT formalism offers an efficient method for studying dc transport in molecular systems.
  • Lattice relaxation due to adatoms is a significant factor influencing the electronic transport properties of graphene.
  • The method provides insights into the interplay between structural modifications and electronic behavior in nanoscale materials.