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Re^2: Very weird HOMO-LUMO values for Silicon nanoclusters..

Siddheshwar Chopra

Dear Vitaly and Alex,
First answering Vitaly: Please find the references for the same. First one is for the electronic gap and second one is for optical gap (higher):

Also it is well known that the bandgap expands when the particle size shrinks. In any case bandgap of Si20 has to be more than the Si24 one; which has not been found in my case.

To Alex Sir::
Sir, no hydrogen termination was done. Mult = 1 was used. I too feel that it could be due to NO hydrogen termination. But need proper understanding of it. If this is the reason, then will NOT terminating with hydrogens, create problems everytime? Please discuss this Sir.


On Wed Apr 16 '14 12:44pm, Alex Granovsky wrote
>Dear Siddheshwar,

>Do you have some more details on the reference Si clusters?
>Was they terminated by hydrogens or not? What was the spin
>state of these reference clusters?

>Kind regards,
>Alex Granovsky
>On Wed Apr 16 '14 10:49am, Siddheshwar Chopra wrote
>>Dear All,
>>I am getting very weird HOMO-LUMO values of Si20 and Si24 nanoclusters, 0.32 and 1.44 eV. I checked them many times. The calculations were run for B3LYP level and using 6-31G basis sets, using UNIQUE coords. Both of these have optimized well. Could anyone help? Si20 should to my knowledge have nearly 5 eV gap which must decrease as cluster size increases.


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