Problems in DIIS Convergence

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Problems in DIIS Convergence

Post by edulsa » 06 Nov 2018, 16:56


I am trying to calculate the optical rotation of an organic compound (C, H, O and Br) starting from x-ray crystallographic data (output is attached). Firstly, I didn't get SCF convergence using default cycles number. To work around this, I rose step number until 1024 (I know, it is a very high value and normally, this wouldn't be needed). But, my problem now is that the calculation is stopped due, I guess, a full storage in scratch partition. In the beginning, there were 325 GB available but file AOTWINT is a 324 GB long. A previous calculation with a molecule of the same size (but without BR) ran smoothly.
Please, I will appreciate any hints to solve this: they can be about how to get the best convergence faster or how to store integrals in RAM memory (I have 16 GB) instead of store them in a hard disk.

Thank you in advance



Dep. Química da Universidade Federal do Paraná - Curitiba - Brazil
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Re: Problems in DIIS Convergence

Post by magnus » 06 Nov 2018, 21:24

You need to run a direct calculation so that two-electron integrals are recomputed when needed and not stored on disk. To do this, add a .DIRECT keyword under the **DALTON INPUT section.

I also note that you have a **SCF INPUT but this section should be added under **WAVE FUNCTION and as *SCF INPUT and not **SCF INPUT. Also I don't think you need such a tight threshold in the SCF, especially considering that you're using a slightly higher than default threshold in the **PROPERTIES part.

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