Quantum Transport Calculations Using PEtot_trans

 
     This is the home page for PEtot_trans. PEtot_trans is developed based on PEtot. It uses plane wave nonlocal pseudopotential
     to study the quantum transport problems. Instead of using the nonequilibrium Green's functions, it generates the scattering
     states (which satisfies the Schrodinger's equation and the proper scattering state boundary conditions). It uses an auxiliary
     periodic boundary condition. As a result, the conventional plane wave expansion techniques can be used. For a given energy E,
     it first generates N "system states", which satisfy the Schrodinger's equation in the centeral regime (but not near the boundary).
     A linear combination of these "system states" are then used to satisfy the scattering state boundary condition, thus to generate
     the scattering states.

     transport.jpg

     Although charge selfconsistent calculations based on the scattering states can be performed, it is not included in this package.
     Nevetherless, an approximate charge selfconsistent treatment is provided. In this treatment, the conventional eigen states are
     partitioned into left scattering part and right scattering part. These two parts are occupied according to left and right electrode
     Fermi energies to get the total charge density of the system. A selfconsistent calculation is performed based on this approximation.

     In order to carry out a transport calculation, several steps must be taken. One needs first to calculate the electrode system, including
     its charge density, potential and Bloch states. Although in our scattering state calculations, currently we only calculate Gamma point
     in the cross section directions, for the selfconsistent field (SCF) electrode calculation, one should include many k-points in the cross
     section direcitons. Then one needs to calculate the central regime. This is the system with the molecule connected by two electrodes,
     but the length of the electrodes can be short, and the electrodes can be ended by vacuums. Nevertheless a bias can be put to the two
     electrodes and a SCF calculation can be carried out with this bias using the approximated method (which breaks a stationary eigen
     states into left and right parts, and occupyies them with different Fermi energies). After we have the central system and the electrodes,
     we will connect them to form the full system (it is also called system). The following calculations are nonselfconsistent calculations using
     the constructed potential of this full system. We first calculate many eigenstates of this full system using a conventional periodic box
     plane wave pseudopotential method. These eigenstates and eigen energies are then used in another special transport code (PEtot_trans2)
     to calculate the "system states" of this system for a given energy E. These system states are then used with the analysis codes to generate
     the scattering states and transmission coefficients.

     The more detailed procedure is described in the following file:

     Transport_how_to

     All source files and examples are included in the follow file (60MB):

     TRANS_ALL_Oct_2011.tar.gz

     The authors of the code:

     Lin-Wang Wang (the original codes and ideas)
     Aran Garcia-Lekue  (the multiple steps)
     Maia Garcia Vergniory (complex band structures, not included in the current version).

    The references:
    (1) L.W. Wang, "Quantum transport calculations using auxiliary periodic boundary conditions", Phys. Rev. B 72, 45417 (2005)
    (2) A. Garcia-Lekue, L.W. Wang, "Elastic quantum transport calculations for molecular nanodevices using plane waves", Phys. Rev. B 74, 245404 (2006)
    (3) A. Garcia-Lekue, L.W. Wang, "Self-consistent non-equilibrium transport using planewaves" Comp. Mat. Sci. 45, 1016 (2009).
    (4) M.G. Vargniory, C. Yang, A. Garcia-Lekue, L.W. Wang, "Calculation of complex band structure for plane-wave nonlocal pseudopotential Hamiltonian",
         Comp. Mater. Sci. 48, 544 (2010).