NanoDCAL is an LCAO implementation coupling density functional theory (DFT) with the Keldysh non-equilibrium Green’s function formalism (NEGF). It is a general purpose tool for ab initio modeling of non-linear and non-equilibrium quantum transport. One may obtain a free license to test NanoDCAL on a single multicore CPU. Unleash the full power and functionality of NanoDCAL by buying a parallel license.
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NanoDCAL is an atomic orbital-based implementation of density functional theory (DFT) coupled with the Keldysh non-equilibrium Green’s function formalism (NEGF). It is a general purpose tool for quantitative calculations of non-linear and non-equilibrium quantum transport properties of two-probe device structures such as:
- molecular electronics (small to large scale systems < 1000 atoms)
- spintronics (collinear / non-collinear / Spin-Orbit Coupling)
- semiconductor nanoelectronics (I-V curve)
- nano-wires and sensors
- carbon nanostructures
- metal contacts and interfaces
- several features such as total energy, force, scattering states and phonons calculations are part of the software suite.
- and other transport junctions
NanoDCAL includes a large suite of methods for calculating many important transport properties in your materials. In addition to transport, typical equilibrium electronic structure calculations can also be done.
A two-probe device is schematically shown in the figure above where a scattering region indicated by "Device" is located between two semi-infinite leads. The leads extend to infinity where external bias voltages are applied, and electric current is collected. The scattering region can be influenced by external physical effects not anticipated by NanoDCAL, as indicated by the "X-probe" in the figure. When required, one can use the NanoDCAL API to include them at the self-consistent level. DFT is used to determine device Hamiltonian H, which gives the electronic states then in turn yields the density matrix. At equilibrium, the statistics are Fermi-Dirac, but when a current flows, NEGF theory is used to determine the non-equilibrium quantum statistical information. NanoDCAL does this by self-consistently solving the NEGF-DFT equations. The leads are simulated atomistically with DFT to provide a complete first principles description of your device.
In NanoDCAL, wavefunctions are expanded in linear combination of atomic orbitals (LCAO) and atomic cores are defined by norm conserving nonlocal pseudopotentials. The LCAO basis and its associated pseudopotentials can be generated by a separate and proprietary atomic package called Nanobase. A database of these potentials and basis functions is provided along with NanoDCAL, but users may also use Nanobase to generate basis functions tailored to their research and design challenges. Its Poisson solver is implemented in real space to handle open device boundary conditions. NanoDCAL is implemented in Matlab and C, for its most computationally intensive components. It is parallelized using MPI to run efficiently on computer clusters.