Setting basis set for electron transfer from CdS into TiO2

[Hamid Mehdipour]

Dear pyxaid users/developer

I am studying electron injection from CdS into TiO2 using NAMD approach. Now I 'm using pyxaid package. Would be possible someone kindly help me with construction of basis set for this process?

30 bands selected for Hamiltonian construction and from this selected band set an active space of [6-13] has been made. 7 is the valence band and 8 to 13 are conduction bands. For initial electronic state I selected -11,-12,-13, one of which could be CdS's LUMO as I found from some preliminary decoherence rate calculations (12 decoherence more rapidly than 9-12).

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params["active_space"] = [6,7,8,9,10,11,12,13]
#Generate basis
statesparams["states"] = []
params["states"].append(["ES1",[6,-6,7,-8]])
params["states"].append(["ES2",[6,-6,7,-9]])
params["states"].append(["ES2",[6,-6,7,-10]])
params["states"].append(["ES2",[6,-6,7,-11]])
params["states"].append(["ES2",[6,-6,7,-12]])
params["states"].append(["ES2",[6,-6,7,-13]])

Initial conditions
nmicrost = len(params["states"])
ic = []

i = 0
while i<100:
j = 3 # started from -11,-12,-13 one of which I believe belongs to CdS (donor semiconductor)
while j<nmicrost:
ic.append([2*i,j])
j = j + 1
i = i + 1
params["iconds"] = ic

Best regards
Hamid

[Alexey Akimov]

Hi Hamid,

If your VBE is the orbital with index 7, then you could define the GS as [7,-7]. The excitations will then be [7,-8], [7,-9], etc. You don't have to occupy 6 and -6, unless you are considering hole dynamics.

By the way, to determine which orbital is CdSe's LUMO, you'd need to look at the orbital localization and pDOS (atomic projections), not at the decoherence rates.

Everything else looks fine.

Best,

Alexey

[Hamid Mehdipour]

Really appreciate it

[Hamid Mehdipour]

Hi Alexey,

Thank you for giving the very brief description of the ground state. Since you pointed out the GS I doubt whether I should include it the charge transfer dynamics. Would we really need to determine here the ground state for electron transfer in the basis set? Electron transfer dynamics is fully associated with excited states.

Really looking forward to hearing your comments/points

Best

Hamid

[Alexey Akimov]

Hamid,

Whether to include the GS in the basis depends on the process you are looking at. If you study electron-hole recombination, you need it. If you look at the electron transfer, you need to find out the localization of each electronic state first (e.g. by analyzing the orbitals or pDOS) and then include just such states in the dynamics. Of course, if you exclude the GS, you may be overlooking the competing process of el-hole recombination. But, if you know it is very slow, it may be a reasonable approximation.

Best,

Alexey

[Hamid Mehdipour]

Hi Alexey,

Thank you for your prompt response and invaluable points. For electron transfer (without GS basis) I got 300 fs and for recombination 50 ps-recombination is 100 time slower. Therefore, adding GS basis into the set would not affect the electron transfer that much.

Best

Hamid