Questions tagged [basis-sets]
For questions about the usage and construction of electronic structure basis sets.
73
questions
4
votes
1
answer
381
views
Kill or let be: Is this calculation stuck or just very slow?
My question is regarding a medium-to-large DLPNO-UCCSD(T)-F12 calculation.
I have a ~250 electron system, an open-shell molecule inside a water droplet, and I'm trying to get the total energy, first ...
- 4,719
5
votes
2
answers
100
views
Explicit form of Hartree Fock analytic gradient with contracted GTOs? With or without density fitting
Does anyone know of a paper, textbook, or other resource which outlines the expression for the analytic gradient of the HF energy (restricted or otherwise) in terms of Dunning's contracted Gaussian-...
- 51
3
votes
0
answers
58
views
How to choose the orientation of basis functions in a Gaussian calculation?
I am trying to run a g09 calculation for a D5h symmetric molecule using the HF/LANL2DZ level of theory. The molecule is pentagonal planar in geometry, and I would like to visualize the canonical ...
- 175
3
votes
1
answer
73
views
How to exploit STO-nG coefficients from basissetexchange (BSE)?
I am trying to understand how to use the data of STO-6G basis from BSE in order to code my own DFT package. I started with a simple DFT code for H2. So the primitive gaussians are of the from : $$\...
- 723
3
votes
2
answers
57
views
How to remove f functions from a cc-pVQZ basis set in CFOUR format?
I need to perform a calculation on a BN system with using cc-pVQZ stripped of the f functions. However, I don't really know how to do this and I have not been able to find a revised one already. I ...
- 536
3
votes
0
answers
144
views
Help with Mathematica for optimizing a Gaussian basis set for a hydrogen atom in a magnetic field
This is a follow-up to my previous question: Optimal Gaussian basis set for hydrogen atom in magnetic field
Brief description of the problem
I would like to find the ground and excited states of the ...
- 233
4
votes
1
answer
125
views
DFT calculation for conjugated polymers
I am new to DFT calculation.
I want to know the structure of conjugated polymers (plane angle, etc.) and their electronic and optical properties (such as HOMO-LUMO, IR, etc.).
I am using 6-311+G(d) ...
6
votes
1
answer
145
views
Optimal Gaussian basis set for hydrogen atom in magnetic field
Copy from here https://mathematica.stackexchange.com/questions/285044/optimal-basis-set-of-gaussian-functions-for-describing-a-quantum-system
This question arose during the discussion of the previous ...
- 233
6
votes
1
answer
76
views
What is the X in Almlöf and Taylor's "Unified treatment of energy derivatives?"
I have been studying the possible methods for basis set optimizations. One notable paper is "Energy-optimized GTO basis sets for LCAO Calculations. A Gradient Approach" by Knut Faegri Jr. ...
- 268
6
votes
1
answer
66
views
Choosing the right basis set for describing vdW-interactions with DFT-D3
I want to do some DFT calculations for structures of protonated alkaloid dimers. I know that a method of choice when vdW interactions are involved is the use of dispersion corrections. But now I am ...
- 563
4
votes
1
answer
264
views
Inputting custom STO-3G basis into PySCF
A simple question about PySCF, but nonetheless I could not find out how to do it: I have a system of atoms for which I already calculated a STO-3G basis in the usual form of MOs:
$$\chi = \sum_i c_i \...
- 95
2
votes
3
answers
129
views
Can I freeze f functions from a TZ basis set during MP2 (but not during H-F) to speed up calculations?
This is another question about my molecule; as I'm not doing this as an academical affiliate(I'm currently majoring in mathematics), I have only NWChem and my personal laptop on the mix, and thus need ...
- 870
7
votes
1
answer
135
views
Mixing pseudopotentials with gaussian and plane wave basis
I am somewhat of a novice in computational chemistry of materials, and have been tasked to replicate simulations from a relevant paper. The paper is a bit scant on details so I am trying to recreate ...
- 481
3
votes
1
answer
26
views
Does the accuracy of RI-MP2 follow the higher number of zetas of the main and fitting bases?
It has been answered to my previous question that RI-MP2/cc-pVTZ/cc-pVTZ gives results of the same quality as MP2/cc-pVTZ. I then started to think about RI-MP2/cc-pVTZ/cc-pVQZ.
The term "basis ...
- 870
4
votes
3
answers
508
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 ...
- 870
7
votes
2
answers
202
views
How does pyscf's internal basis format distinguish between 1s and 2s orbitals?
For example: gto.basis.load("6-31g", "Li") will show:
...
- 231
5
votes
2
answers
274
views
Do the cc/pc/def2 basis sets mathematically converge to the CBS limit, assuming exact CI/DFT?
The cc-, pc- and def2- basis sets are often described as "systematic", in the sense that the results of these basis sets at different cardinal numbers (i.e. the number of ζ's) can be ...
- 870
5
votes
1
answer
808
views
Choosing between 6-311++G(3df,3pd) and def2-TZVPPD for certain type of diffuse system
I need to use a diffuse basis set for my highly delocalised molecule, consisting of C, N, O, Cl, S, Mg, Al, B and Si only, since it has many non-covalent interactions inside it. After reading some ...
- 870
8
votes
2
answers
345
views
Basis Set to analyze a molecule that involves silver
I am a bit new to computational chemistry, but I've been looking into a reaction of a molecule that contains C, H, and F reacting with AgF in a polar solvent. I am looking into one pathway that ...
- 183
6
votes
1
answer
2k
views
How to add different basis sets to different atoms in a calculation (Gaussian 16) when freezing certain atoms?
I am using Gaussian 16 to optimize a paraquat molecule on top of a bulk of gold atoms. Some of these gold atoms are frozen, so I use the option opt=modredundant. I ...
- 133
5
votes
1
answer
168
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 ...
- 125
6
votes
1
answer
146
views
How exactly are valence orbitals combined in split valence basis sets such as 3-21G?
For hydrogen, the 3-21G basis set (in CFOUR format) is
...
- 231
9
votes
1
answer
548
views
How to build cartesian representations of spherical Gaussian basis functions?
I'm trying to code an integral library for my own QC software from scratch. I need to use the spherical basis functions like in any other popular program. So, a D basis function is supposed to make ...
- 133
5
votes
1
answer
138
views
How are the exponents in a STO-nG basis set obtained?
STO-3G has exponent parameters which can be found in a reference book. Can these parameters be calculated using, for instance, a Hartree–Fock equation for one atom? Or using another way?
- 877
9
votes
1
answer
273
views
Basis sets optimized for CCSDT(Q) calculations
CCSDT(Q) and CCSDTQ calculations are extraordinarily expensive, both in terms of FLOP count and RAM capacity requirements, eg. CCSDTQ requires a computational effort that scales as ~$N^{10}$, where N ...
- 375
7
votes
1
answer
54
views
Any molecular codes to calculate non-local susceptibility?
I am interested in calculating the non-interacting non-local susceptibility for simple molecules.
In principle, if you have a single Slater determinant, then you should just take a sum over the ...
user4626
5
votes
1
answer
93
views
About the order of indices in basis set expansion
In many books, e.g., Szabo and Ostlund, Helgaker Jorgensen and Olsen, etc etc, the expansion of Hartree-Fock orbital by basis set is written as a kind of
$$
\phi_i = \sum_{\mu} C_{\mu i} \chi_{\mu}
$$
...
- 182
9
votes
3
answers
361
views
The number of orbitals in Gaussian/GAMESS log file
After calculating the energy of a $\ce{CH4}$ molecule with a 6-31G(d,p) basis set, I obtained the Gaussian/GAMESS log file and describe a part of the log file as follows.
...
- 1,779
5
votes
2
answers
518
views
The format and values provided by Basis Set Exchange
In this question and answers, I found that Basis Set Exchange provides information about the orbitals (e.g., the orbital exponents and contraction coefficients). For example, the following example is ...
- 1,779
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 ...
- 1,779
11
votes
1
answer
557
views
What is the minimum basis set one should use?
If I'm interested in getting an answer that is minimally correct what is the minimum basis set level I should use? (i.e. anything less would be much less reliable)
Obviously this depends on the ...
- 7,957
5
votes
0
answers
68
views
How to get energy eigenstates using plane wave basis wavefunction .hdf5 output from Quantum ESPRESSO? [closed]
When compiled with the HDF5 flag on, Quantum ESPRESSO (QE) saves wavefunctions in the .save folder. At each k-point, we have an $m\times n$ matrix, where $m$ are the complex number entries of ...
- 2,281
8
votes
1
answer
246
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 ...
- 481
10
votes
1
answer
717
views
Molecular orbitals and active space
During the same minute as asking this question, I also asked this at Quantum Computing SE.
In Qiskit, each qubit corresponds to one spin orbital. For example, the $\ce{N2}$ molecule would have 10 ...
- 435
8
votes
2
answers
2k
views
Is the number of basis functions same in the different atoms in the 6-31G basis set?
I'm now studying the quantum chemistry calculation and Gaussian basis set.
For example, when using the 6-31G basis set,
the C atom has 6 basis functions in 1s orbital:
3+1=4 in $2s$,
3+1=4 in $2p_x$,
...
- 1,779
11
votes
2
answers
1k
views
Critical difference and roles of Slater- and Gaussian-type orbitals
I was very interested in the following question and answer about the Slater- and Gaussian-type orbitals (STO and GTO) used in quantum chemistry and a practical calculation.
Gaussian-type orbitals vs ...
- 1,779
11
votes
0
answers
115
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 ...
- 2,363
7
votes
2
answers
153
views
What quantity to perform CBS extrapolation on for adsorption/binding energies?
When calculating complete basis set extrapolations for quantities, such as adsorption energies or binding energies, which depend on the difference between three quantities (i.e. $E_\textrm{prop} = E_\...
- 398
10
votes
2
answers
129
views
How to create a differential spectrum from two simulated spectra, calculated by two different basis sets?
In my bachelor thesis, I compare simulated IR-spectra computed by different basis sets. The simulated spectra from sets like cc-pVTZ and cc-pVQZ are too similar to compare them by plotting them next ...
- 589
8
votes
1
answer
70
views
PES of Tetramethylthiuramdisulfid / Problem with Disulfidbridge
I like to perform a DFT Study on Tetramethylthiuramdisulfid. So I made a structure optimization for my start structur with PW6B95D3/aug-cc-pvtz to get a good structure to begin my dihedral scan to get ...
- 816
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 ...
- 841
9
votes
1
answer
285
views
How are molecular orbitals constructed from the coefficients and basis set?
When an SCF calculation is done in a QM program, the MO coefficients of the solution are printed into the output. Now, graphical softwares can plot 3D molecular orbitals from these coefficients, ...
- 6,551
14
votes
1
answer
143
views
What are the physical consequences of adding a constant to the diagonal of the effective Hamiltonian of monolayer materials?
Effective Hamiltonians modeling many-layered materials are often tuned using some sort of bias voltage. For instance, in a $4\times 4$ Hamiltonian matrix to describe biased bilayer graphene using some ...
- 2,281
17
votes
3
answers
781
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 ...
- 6,551
15
votes
3
answers
690
views
How should I compare different basis sets for post-Hartree-Fock methods?
HF or DFT methods are variational so I can confidently say that any basis set that gives the lowest energy is the best for that system. However, I have learnt that post-HF methods such as MP2, MP3, ...
- 6,551
11
votes
1
answer
129
views
Is it possible to make segmented contracted basis sets for correlated calculations?
The segmented contracted basis sets are usually handled well by the QM programs than generally contracted basis sets, as the primitives are not repeated. The correlation consistent basis sets (cc-PVnZ)...
- 6,551
14
votes
1
answer
283
views
Is basis set superposition error reduced when using the GAPW method?
CP2K implements the Gaussian and Augmented Planewaves (GAPW) approach for all-electron calculations. My understanding is that the GAPW method involves using atom-centered Gaussian type orbitals to ...
- 890
16
votes
2
answers
557
views
What's the best way to compare two DFT codes?
What's the most efficient way to compare the two DFT codes in terms of computation time, basis sets (for example, one plane wave vs one atomic orbitals), functional performance, etc.?
- 1,041
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, ...
- 6,551
14
votes
2
answers
381
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,...
- 741