[CP2K-user] [CP2K:20351] Re: Lower LUMO energy than occupied molecular orbitals in OT calculations

[mshakiba.k...@gmail.com]

Thank you very much for the interesting and important suggestions. We will 
test them.

Best,
Mohammad.

On Wednesday, June 19, 2024 at 12:59:45 AM UTC-4 Marcella Iannuzzi wrote:

> Hi ..
>
> If the system has no or very small gap, OT can fail and end up into a 
> wrong state.
> The calculation of the virtual states is done a posteriori, using the 
> Hamiltonian obtained by OT,  this is the reason of the weird order. 
>
> For such a system the diagonalization is a safer optimisation method, but 
> proper mixing in G-space, with small mixing coefficient, and smearing need 
> to be used. 
> By convergence problems, reducing the mixing parameter and increasing the 
> electronic temperature helps.
>
> Other remarks: the pw-cutoff is far too low, the number of grids is 
> unnecessary large (4-5 should be enough), if the material has magnetic 
> properties it might be necessary to initialise the magnetisation of 
> specific elements and the corresponding multiplicity. 
>
> Regards
> Marcella
>
>
> On Wednesday, June 19, 2024 at 1:49:00 AM UTC+2 mshakiba.k... at gmail.com 
> wrote:
>
>> Dear CP2K developers,
>>
>> Hi, We are running a calculations for Cd33Se33 with Ferrocine ligands 
>> (containing Fe). The input and the structure are attached. However, when 
>> running a single-point calculations we face multiple problems. The first 
>> thing is that the &DIAGONALIZATIO approach does not converge and it gives 
>> large convergence values (like 100, 200, etc). Changing the basis set to 
>> DZVP or even TZVP did not have any effect on this procedure. We also tried 
>> adding smearing, increasing the cutoff, lowering the EPS_DEFAULT etc but no 
>> effects on the convergence. 
>>
>> So, we started using the OT procedure and it converged the results in a 
>> large number of steps (about 500). However, when printing out the energy 
>> levels, we see that the LUMO energy is lower than the occupied orbitals 
>> including HOMO, HOMO-1, HOMO-2, and HOMO-3. The results seem to be no 
>> physical at all. So, even trying with unrestricted case, we get a similar 
>> thing. Is this a problem of the OT procedure? Because the diagonalization 
>> should print the eigenvalues in ascending order but in this case they are 
>> not. We appreciate any suggestions to helps us understand the problem. 
>>
>> Thank you in advance.
>>
>> The attached files are the input, the coordinates, and one sample pdos 
>> file showing the energies of the molecular orbitals.
>>
>

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