Dear all,
There are two questions that confused me about my recent work, and I need your help:
In my Metal-Molecule-Metal molecular junction(MMMs, or two-probe system), when calculates the EnergySpectrum of molecule in central region(ATK Version 2008), I've written down the atomic indices of atoms which formed the molecule, and uncheck the two CheckBoxs(Am I right to calculate the EnergySpectrum?) .
1)I first calculted the EnergySpectum naked molecule(in GGA.PBE exchange correlation potential),the QuantumNumbers of HOMO&LUMO are 254&255, respectively. However, when put into MMMs(weak coupling, in GGA.PBE exchange correlation potential), the two quantumNumber became 224&225, meanwhile, almost all the energy level of orbitals shift up ~4.7eV. So my question is whether the QuantumNumbers of HOMO&LUMO are 254&255 or 224&225 when calculates the MPSH of MMMs? What causes such upshift?
2)Through calculating the MullikenPopulation of central region, I found that the charges transferred from metal leads to the molecule under equilibrium circumstance, and the HOMO&LUMO asymmetrically aligned relates to FermiLevel of equivalent bulk markedly(LUMO closed to EF) at 0 bias. Is the alignment related to the charge transfer? In my several calculated systems, even the numerical values of transferred charge become smaller, the asymmetrical alignment had not significant change, why?
Thank you very much!
Sincerely.
