Energy Cut off(s) in Gaussian 09 PBC calculations

In summary, the conversation involves a PhD student working on a project using DFT calculations to study adsorption of molecules on mineral crystals. They are using the Gaussian 09 simulation package and are currently in the starting stage of modeling their crystal lattice. They mention the importance of mentioning k points and energy cut offs in calculations and ask for help in varying the cutoff energy for a PBC calculation in Gaussian 09. They also inquire about the default energy cut off used by Gaussian 09. It is noted that Gaussian 09 does not use energy cutoffs as it uses Gauss-type orbitals instead of plane waves.
  • #1
chowdhry
3
0
Hello Everyone,

I am a PhD student working in the field of mineral and material processing. One part of my project involves use of DFT calculations to study adsorption of small to mid sized molecules on mineral crystals.

I am using Gaussian 09 simulation package and currently I am in the starting stage of modeling my crystal lattice. I believe that it is always important to mention k points and energy cut offs used in one's calculations and to find the optimum values for both in the start of any such calculations

But I couldn't find how I can vary the cutoff energy for a PBC calculation in Gaussian 09.

If some body can help me in this I would be highly obliged. Also, if anyone know the default energy cut off Gaussian 09 uses please let me know.

Thanks.
Chowdhry
 
Physics news on Phys.org
  • #2
Gaussian does not use plane waves to expand crystal orbitals, but Gauss-type orbitals. Gauss orbitals do not have energy cutoffs.
 

1. What is the purpose of energy cut off(s) in Gaussian 09 PBC calculations?

The energy cut off(s) in Gaussian 09 PBC (Periodic Boundary Conditions) calculations are used to define the maximum energy threshold for including basis functions in the calculation. This helps in reducing the calculation time and increasing the accuracy of the results.

2. How do I determine the appropriate energy cut off(s) for my Gaussian 09 PBC calculation?

The appropriate energy cut off(s) for a Gaussian 09 PBC calculation depends on the size of the system being studied and the desired level of accuracy. A general rule of thumb is to choose a value that is at least twice the highest occupied molecular orbital (HOMO) energy for open-shell systems, and at least twice the highest virtual orbital energy for closed-shell systems.

3. Can I use different energy cut off(s) for different types of atoms in a Gaussian 09 PBC calculation?

Yes, Gaussian 09 PBC calculations allow for the use of different energy cut off(s) for different types of atoms. This can be specified in the input file by using the keyword "PBC" followed by the energy cut off(s) value for each atom type.

4. What happens if the energy cut off(s) used in a Gaussian 09 PBC calculation is too low?

If the energy cut off(s) used in a Gaussian 09 PBC calculation is too low, basis functions with energies above the cut off will be excluded from the calculation. This may result in inaccurate or unreliable results.

5. Is there a maximum limit for energy cut off(s) in Gaussian 09 PBC calculations?

There is no specific maximum limit for energy cut off(s) in Gaussian 09 PBC calculations. However, using very high energy cut off(s) values may lead to increased computational time and memory usage without necessarily improving the accuracy of the results.

Similar threads

How to Calculate Ideal Gas State Properties Using Molecular Dynamics?
    • Chemistry
Replies
2
Views
1K
I How to solve 2nd order TDSE for a Gaussian-kicked harmonic oscillator?
    • Quantum Physics
Replies
6
Views
1K
1000 Basis functions limitation - Gaussian 09?
    • Quantum Physics
Replies
2
Views
2K
Calculate Si cohesive energy using VASP
    • Atomic and Condensed Matter
Replies
1
Views
7K
Understanding DFT to Calculate Potential Energy of Atoms
    • Atomic and Condensed Matter
Replies
4
Views
5K
Cut-off energy of Be having HCP structure
    • Advanced Physics Homework Help
Replies
3
Views
1K
Calculate the "surface energy" of succesively smaller cubes
    • Biology and Chemistry Homework Help
Replies
3
Views
2K
Change in Free Energy when Heating a Substance
    • Chemistry
Replies
9
Views
2K
I Solving simultaneous vector equations
    • General Math
Replies
11
Views
1K
Calculating time to reduce alcohol in wine using heating method
    • Chemistry
4
Replies
131
Views
4K

Hot Threads

Recent Insights

Back
Top