At first, `openmx`

calculate the transmission, the total current,
and the conductance.
The input parameters for this calculation are as follows:

NEGF.tran.Analysis on # default on NEGF.tran.CurrentDensity on # default on NEGF.tran.energyrange -10 10 1.0e-3 # default=-10.0 10.0 1.0e-3 (eV) NEGF.tran.energydiv 200 # default=200 NEGF.tran.Kgrid 1 1 # default= 1 1

`NEGF.tran.Analysis`

,`NEGF.tran.Channel`

,`NEGF.tran.CurrentDensity`

If

`NEGF.tran.Analysis`

is set to`on`

, the transmission, the total current, and the conductance are calculated.`NEGF.tran.energyrange`

,`NEGF.tran.energydiv`

The energy range where the transmission is calculated is given by the keyword 'NEGF.tran.energyrange', where the first and second numbers correspond to the lower and upper bounds, and the third number is an imaginary number used for smearing out the transmission. The energy range specified by 'NEGF.tran.energyrange' is divided by the number specified by the keyword 'NEGF.tran.energydiv'.

`NEGF.tran.Kgrid`

The numbers of

**k**-points to discretize the reciprocal vectors and are specified by the keyword 'NEGF.tran.Kgrid'. The set of numbers given by 'NEGF.tran.Kgrid' can be different and tends to be larger than that by 'NEGF.scf.Kgrid' because of computational efficiency.

In the calculation of the transmission, the current, and the conductance, following messages are printed in the standard output.

******************************************************* ******************************************************* Welcome to TRAN_Main_Analysis. This is a post-processing code of OpenMX to analyze transport properties such as electronic transmission, current, eigen channel, and current distribution in real space based on NEGF. Copyright (C), 2002-2015, H. Kino and T. Ozaki TRAN_Main_Analysis comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under the constitution of the GNU-GPL. ******************************************************* ******************************************************* Chemical potentials used in the SCF calculation Left lead: -5.125617225230 (eV) Right lead: -5.125617225230 (eV) NEGF.current.energy.step 1.0000e-02 seems to be large for the calculation of current ... The recommended Tran.current.energy.step is 0.0000e+00 (eV). TRAN_Channel_kpoint 0 0.000000 0.000000 TRAN_Channel_energy 0 0.000000 eV TRAN_Channel_Num 5 Parameters for the calculation of the current lower bound: -5.125617225230 (eV) upper bound: -5.125617225230 (eV) energy step: 0.010000000000 (eV) imaginary energy 0.001000000000 (eV) number of steps: 0 calculating... myid0= 0 i2= 0 i3= 0 k2= 0.0000 k3= -0.0000 myid0= 1 i2= 0 i3= 0 k2= 0.0000 k3= -0.0000 Transmission: files ./negf-chain.tran0_0 Current: file ./negf-chain.current Conductance: file ./negf-chain.conductance

After the calculation, in this case you will obtain three files
`negf-chain.tran0_0`

,
`negf-chain.current`

,

`negf-chain.conductance`

:

*System.Name*.tran#_%The file stores transmissions for up- and down-spin states. The fourth column is the energy relative to the chemical potential of the

**left**lead, and the sixth and eighth columns are transmission for up- and down-spin states, respectively. When you employ a lot of**k**-points which is given by 'NEGF.tran.Kgrid', a file with a different set of '#' and '%' in the file extension is generated for each**k**-point. The correspondence between the numbers and the**k**-points can be found in the file.*System.Name*.currentThe file stores

**k**-resolved currents and its average for up- and down-spin states in units of ampere.*System.Name*.conductanceThe file stores

**k**-resolved conductance at 0 K and its average for up- and down-spin states in units of quantum conductance ( ). Thus, the conductance is proportional to the transmission at the chemical potential of the**left**lead, , as follows:

As an example, the **k**-resolved transmission drawn by
using the file '*System.Name*.conductance' is shown in Fig. 33.

2016-04-03