homo and lumo gap

[shabnam borji]

Hi，everyone！

I try to calculation the molecular orbitals (MOs) of a semiconductor. my calculations produced a series of cube files of MOs.

HOMO and LUMO energy are close to the values in article but the HOMO-LUMO gap is very smaller than experimental values.

calculated gap = 2.840 ev

experimental = 6 ev

can anyone give me some suggestions about my calculation? attached are my input and output files.

[Lucas Lodeiro]

Hi.

I can not see your file in my cellphone... But I guess, the band gap subestimation is due to the GGA functional used... This is a typical error of GGA... You can improve it using hybrid functionals o GW approximation. If your system is a solid, HSE functional could give you a very good gap... For a molecule organic B3LYP. That is as a first glance. The particular literature about your topic and material is important too.

Regards

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[shabnam borji]

Dear Lucas

Thank very much for your reply. I will try this.

Best

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[shabnam borji]

Hi,

I searched GW method and find an input for this type of calculation.

This input working for a small molecule like water but my system is a polymer with a number of monomers.

when I try this input for one monomer this worked and HOMO-LUMO gap estimate near the experimental values but with two monomers or more, calculation failed by this error:

 RI-RPA section
 --------------

  Used number of processes per group:                                          1
  Maximum allowed memory usage per MPI processes:                    1024.00 MiB
  GPW_INFO| Density cutoff [a.u.]:                                         150.0
  GPW_INFO| Relative density cutoff [a.u.]:                                 25.0
  RI_INFO| Cholesky decomposition group size:                                  1
  RI_INFO| Number of groups for auxiliary basis functions                      8
  RI_INFO| Occupied  basis set size:                                          31
  RI_INFO| Virtual   basis set size:                                         979
  RI_INFO| Auxiliary basis set size:                                        3300
  RI_INFO| Total memory for (ia|K) integrals:                         764.10 MiB
  RI_INFO| Total memory for G0W0-(nm|K) integrals:                    508.58 MiB

===================================================================================
=   BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
=   PID 28187 RUNNING AT physchem-System-Product-Name
=   EXIT CODE: 9
=   CLEANING UP REMAINING PROCESSES
=   YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
===================================================================================
YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Killed (signal 9)
This typically refers to a problem with your application.
Please see the FAQ page for debugging suggestions

Do you have any solution for this?

I attached my input and output files in txt format

On Sun, Dec 29, 2019 at 6:19 AM Lucas Lodeiro <eluni...@gmail.com> wrote:

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[Lucas Lodeiro]

Hi. I do not know why this error appears, but if your system is a big system, with 50 or more atoms, the GW method is not the best for you, due to the computational cost. In this case I would prefer an hybrid functional or a pos-calculation correction of homo lumo with a highest level of theory, as the GW over the monomer.

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[shabnam borji]

In cp2k tests or exercises there are any samples of pos-calculation correction theory input?

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[Thomas Kühne]

Dear Shabnam, 

don’t forget the memory requirement to store the necessary 

integrals when going to more complex systems! I suspect 

that you may be running out of memory … 

Cheers, 

Thomas

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<input.txt><1mono.txt><2mono.txt>

==============================

Thomas D. Kühne

Dynamics of Condensed Matter

Chair of Theoretical Chemistry

University of Paderborn

Warburger Str. 100

D-33098 Paderborn

Germany

tdku...@mail.upb.de

+49/(0)5251/60-5726