[DFTB-Plus-User] Optimizing polyyne chain in DFTB+ for low BLA range: Need guidance

[Khadidja Chaib Edderraa]

Dear ,

I hope this email finds you well. I am currently working on optimizing a
polyyne chain using DFTB+ and aiming to achieve a low range of bond length
alternation (BLA) in my system. After exploring the available resources, I
believe your expertise in DFTB+ could provide valuable insights and
guidance for my research.

To provide some context, my research focuses on  ensuring that the
molecular structure represents the most stable configuration and optimizing
the polyyne chain is crucial for achieving BLA values  that align closely
with experimental and other simulation data.

The specific details of the polyyne chain I'm studying are as follows:
- Number of carbon atoms: 2 carbon
- Parameterisation data (Slater-Koster files)  used to perform calculations
: 3ob, mio, ob2, matsi
- Geometry optimization:  using  conjugate gradient algorithm but have not
obtained the desired results.

My main questions are as follows:
1. What are the recommended optimization settings or parameters for a
polyyne chain in DFTB+ to achieve a low BLA range?
2. Are there any specific convergence criteria that I should consider
during the optimization process?
3. Are there any DFTB+ features or functionalities that could be
particularly useful for optimizing polyyne chains and reducing the BLA
range?

Thank you very much, and I look forward to your response.

Sincerely,
Khadidja
k.chaibedderraa at univ-chlef.dz
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