Dea Yan,

Kpm method is applied for a finite system as mentioned in the documentation:

*hamiltonian* : FiniteSystem https://kwant-project.org/doc/1/reference/generated/kwant.system.FiniteSystem.html#kwant.system.FiniteSystem or matrix Hamiltonian

If a system is passed, it should contain no leads.

Regards,

Adel

On Tue, May 14, 2019 at 6:00 AM X.F.Yan yxf0125@aliyun.com wrote:

Dear Anton and other Kwant users,

Recently, I attempt to use Kwant to calculate the density of states in transport system. I successfully calculated the dos of a large closed system according to the manual. Unfortunately, I use the method to compute the dos of an open system(i.e. a system composed of a scattering region and leads):

fsyst = make_syst().finalized()

spectrum = kwant.kpm.SpectralDensity(fsyst)

energies, densities = spectrum()

But, the system generates a complexwarning :

\Anaconda3\lib\site-packages\numpy\core\numeric.py:501: ComplexWarning: Casting complex values to real discards the imaginary part

return array(a, dtype, copy=False, order=order)

Hence, there’s something wrong with the calculation. I don’t know how to solve the warning.

Please help me solve my bewilderment , Thanks!

Best regard,

Yan