Questions tagged [optimization]

For questions related to theory or application of optimization techniques in matter modeling. If your question is about a specific type of optimization like geometry optimization, we have the "geometry-optimization" and "geometry" tags. Another related tag is the "numerical-convergence" tag.

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How to solve "step out of bounds" error in Gaussian?

I am trying to optimize a molecular geometry with Gaussian 16 and this is the line of instructions: ...
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5 votes
0 answers
34 views

How does TD-DFT optimization proceeds in Gaussian?

I am ambiguous in understanding how does Gaussian actually run the TD-DFT optimization. For the explanatory purposes I attach two files: td=triplets.log, which ...
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6 votes
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Optimizing (DFT/MP2) small molecule dimers

I'm attempting to optimize n-alkane dimers using MP2/DFT in Gaussian09. However the first one or two frequencies are always negative. Can these modes be ignored or do I need to do a tighter ...
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6 votes
2 answers
115 views

Relation between lattice parameter and energy for relaxations

We have been wanting to do relaxation of lattice parameters as a function of the energy. I want to know the mathematical expression for this, and also the theoretical background related to this method....
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11 votes
1 answer
207 views

What's the Theory Behind Nudged Elastic Band?

I'm interested in doing some calculations to model the interstitial addition of nitrogen into a structure and I'm thinking of using Nudged Elastic Band to do it. From what I have read you start with ...
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5 votes
1 answer
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What's the Difference between Lattice Statics and Lattice Dynamics?

For example, in something like the General Utility Lattice Program, you perform structural optimisation and then use phonons to calculate properties like elastic constants etc. The latter part seems ...
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3 votes
1 answer
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How to do lattice optimization, encut optimization and Kpoint optimization in VASP?

What is the procedure to do lattice optimization, encut optimization and kpoint optimization in VASP? Thank you in advance.
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4 votes
1 answer
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How much energy difference could be used to distinguish optimized results from different initial geometries for the same structure?

Is there a threshold? Could I say that my final geometries are the same with 'energy difference = 0.05 meV/atom' ?
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9 votes
1 answer
538 views

How to extract lattice constants a and c from relaxed hexagonal structure using VASP?

Taking a bulk WS$_2$ (bilayer) structure and relaxing it with ISIF=3 and IVDW=10 (DFT-D2 method) using the VASP code. Then ...
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  • 5,511
18 votes
2 answers
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What is the cutting edge for open-source Force-Field generation?

The adoption of atom-typing allowed for the creation of incredibly widely used force-fields (FF) such as GROMOS/AMBER/OPLS and many more. Because of the assumptions ...
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  • 4,066
13 votes
2 answers
550 views

How much does the initial geometry affect the final geometry in optimization calculations?

This might be a stupid question but to what extent will the initial configuration of a bulk phase geometry optimization calculation affect the final geometry? Most places say to start with ...
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15 votes
2 answers
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What exactly is the "Optimizer" in CP2K geometry optimization?

I'm just now starting to use the program CP2K, and I am having trouble understanding the difference between the optimizer options (CG, BFGS, LBFGS). I have seen ...
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17 votes
2 answers
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Is it necessary to optimize structures obtained from a cif file?

Crystallographic Information Files (CIF) are, in general, obtained from experimental measurements. Since the information originated from real samples, is it mandatory to relax the structure in order ...
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11 votes
1 answer
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Hexagonal lattice optimization

I have downloaded POSCAR file for "WS2" from "materials project website". I want to do lattice optimization, draw "Energy versus lattice parameters" curves, and calculate Bulk modulus through Birch–...
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28 votes
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Where/when did the fields of Operations Research and Spin Physics or Molecular Dynamics begin to cross-pollinate?

Operations Research is a field of mathematics in which optimal or near-optimal solutions are sought for complicated problems. In the modeling of materials, we often optimize Ising models, in which the ...
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