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Questions tagged [basis-sets]

For questions about the usage and construction of electronic structure basis sets.

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13 votes
2 answers
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What are the scientific justifications of the binding energy equation?

There are many problems where we want to calculate the binding energy between two systems. Normally, we have a system A, adsorbent (a surface, a nanotube, a protein, etc.), that interact with a system ...
Camps's user avatar
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33 votes
3 answers
1k views

What are the positives and negatives of periodic DFT codes that don't use plane-wave basis sets?

Most periodic density functional theory (DFT) codes use plane-wave basis sets in conjunction with three-dimensional periodic boundary conditions. In contrast, for molecular systems of finite size, ...
Andrew Rosen's user avatar
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20 votes
1 answer
313 views

Are plane-wave basis sets reliable for modeling adsorption processes?

Plane-wave basis sets are useful in the calculation of periodic systems and can be used in combination with pseudopotentials. However, when dealing with surfaces the system is no longer periodic in, ...
Verktaj's user avatar
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18 votes
3 answers
432 views

How trustworthy is the Tran-Blaha modified Becke-Johnson potential and how does it perform across basis sets?

When modeling solid-state materials and particularly semiconductors, one must go beyond LDA and GGA. One alternative is to use hybrid functionals or the $GW$ method. However, this can be very ...
Etienne Palos's user avatar
12 votes
2 answers
148 views

Avoiding charge-migration in electronic structure calculations with solvent-like environments

When performing electronic structure calculations on a molecule, one can surround it with point charges to mimic a solvent environment, and lend polarization effects. There is a bit of a caveat ...
B. Kelly's user avatar
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10 votes
4 answers
1k views

How can I find the parameters in a basis set?

I have a question about the basis functions of Gaussian. When the basis function is set (e.g., 6-31G), I would like to know the specific value of Gaussian's parameters for each atom. In particular, I ...
neco's user avatar
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9 votes
3 answers
1k views

Which software is good with generally contracted basis sets?

Recently, I learnt that basis sets can be contracted as segmented (like def2 or 6-31G) or general (like cc-PVTZ, or ANO). The general contraction allows all the primitives to appear in all shells, ...
S R Maiti's user avatar
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23 votes
5 answers
616 views

What functions other than Gaussians are used for orbital basis sets?

The Gaussian function $\propto\exp((x-a)^2/b)$ with $b>0$ is one of the most common functions used in molecular modelling (e.g. Gaussian type orbitals). What are some examples of applications of ...
TheSimpliFire's user avatar
23 votes
1 answer
171 views

Which basis set families were optimized to give the lowest possible variational energy for a given number of orbitals?

Dunning's basis set families (such as cc-pVXZ and aug-cc-pCVXZ) were not optimized to give the lowest variational energy for a given number of orbitals. For example the S-type orbitals are optimized, ...
Nike Dattani's user avatar
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17 votes
3 answers
631 views

How is "basis set projection" done?

I recently came across something called the basis set projection in Q-chem's manual. What it seems to do is to take the converged SCF in a smaller basis set, and then "projects" that onto a ...
S R Maiti's user avatar
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16 votes
1 answer
2k views

Gaussian-type orbitals vs Slater-type orbitals in terms of computational efficiency

When creating molecular orbitals via the linear combination of atomic orbitals method I am told that Slater orbitals provide a more accurate representation whilst Gaussian orbitals are computationally ...
DJA's user avatar
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16 votes
1 answer
226 views

What methods can be used to calculate excited-states in molecular crystals?

In periodic systems plane-wave basis functions are often used. In a previous question on this site it was questioned if plane-wave basis-sets are reliable for modeling adsorption-processes The ...
Cody Aldaz's user avatar
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14 votes
2 answers
339 views

Optimization of Gaussian basis sets within the Hartree-Fock Method

I am revisiting some exercises in Thijssen's Computational Physics book, particularly chapter 4 on the Hartree-Fock method. I am interested in the method of nonlinear optimisation for its own purposes,...
tmph's user avatar
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14 votes
2 answers
584 views

When are atomic-orbital-basis (rather than plane-wave) methods appropriate in periodic DFT?

For example, GPAW supports both plane-wave and atomic-orbital basis methods. I know that atomic-orbital basis methods can have difficulty with electrons occupying vacancies for example, but what ...
Tristan Maxson's user avatar
11 votes
0 answers
111 views

Should augmented basis be used for Hirshfeld charges? [closed]

I'm calculating condensed Fukui functions to explain the reactivity of my molecules. The manual for Multiwfn suggests using atomic dipole moment corrected Hirshfeld charges for it. However I get ...
roma ichenko's user avatar
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8 votes
1 answer
573 views

Which basis set should be used for a system that contains both anions and cations?

I am trying to model a system that has both anions and cations interacting with each other. (In this case it is calcium ion interacting with two small carboxylic acid molecules). Now, looking through ...
S R Maiti's user avatar
  • 6,276
8 votes
1 answer
223 views

Difference between original STO-3G and BSE STO-3G

I am trying to work with the STO-3G basis set, but I noticed that the STO-3G in Basis set exchange is different from the STO-3G originally published, and not only that, the BSE version seem to be ...
ipcamit's user avatar
  • 481
5 votes
1 answer
137 views

What is the best algorithm for ERIs of contracted gaussian atomic orbitals

I am currently working on python script that does Hartree-Fock-Calculations. I try to avoid packages as good as possible. I've figured out how to calculate the one electron integrals when it comes to ...
lela2011's user avatar
  • 125
4 votes
3 answers
444 views

Does the RI method actually accelerate basis convergence of MP2, "by one more zeta"?

It is often said that the resolution of the identity (RI) method accelerates the basis set convergence rate of MP2 "by one more zeta", e.g. that RI-MP2/cc-pVTZ/cc-pVTZ results are close to ...
Kanghun Kim's user avatar