# Tag Info

Accepted

### Why is my hydrogen energy not equal to -0.5 hartrees?

Yes, the exact orbital energy of the hydrogen atom is $-1/2\ E_h$. The problems in the calculation are as follows. First, you are running ROKS. ROKS has many definitions in the literature; PySCF ...
• 19.7k

### Why is my hydrogen energy not equal to -0.5 hartrees?

The exact non-relativistic ground state electronic energy of a hydrogen-like atom, assuming that the nucleus is "clamped", point-sized, and with an infinitely large mass compared to the mass ...

### Finding HOMO/LUMO from SCF calculation: VASP

No, the HOMO is the highest energy eigenvalue for the corresponding band, across the Brillouin zone. It isn't technically a HOMO because it isn't a molecular orbital ("MO") it's a band, so ...
• 8,022
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### What is the correct way to set up occupation for single atom in CFOUR software?

Your setting is incorrect for the dominant Slater determinant when calculating the electronic ground state of an O atom: OCCUPATION=2-1-1-1-0-0-0-0/2-1-0-0-0-0-0-0 ...

### Is the electron-electron interaction to blame, for the added complexity of using "orbitals" for an N-electron system?

Interpreting the question For a 1-electron system, wavefunctions and orbitals are the same thing. For a 2-electron system, or any N-electron system with N>1, we can use "orbitals" to ...
Accepted

### Orthonormality of AOs and MOs in PySCF

Solving the Hartree-Fock equations is equivalent to unitary rotations of the orbitals, but you are missing the key piece: before Hartree-Fock, the basis set is orthonormalized to produce an ...
• 19.7k
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### How to orthonormalize a set of Molecular orbitals?

Since S is created from orthonormal orbitals, it has 1.00 as diagonal elements. If ${\bf S}$ is created from orthonormal orbitals, the overlap matrix is simply the unit matrix, ${\bf S}={\bf 1}$. ...
• 19.7k
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### Verifying periodicity of crystalline orbital modulus in PySCF

Setting the unit='Bohr' flag in gto.M (as originally suggested in the comments) resolved the issue in the latest version of the ...
• 61
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### Does the relaxed density (and therefore the relaxed orbitals) depend on the final energy in OO-DHDF+D calculations?

The DFT-D family of corrections, including DFT-D2, DFT-D3 and DFT-D4, are energy corrections that depend on the atomic coordinates but not the wavefunction. (The DFT-D4 energy does depend on atomic ...
• 9,670
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### How is the LUMO lower energy than the HOMO for triplet state restricted-open shell DFT calculation?

It would be better to use the word SOMO (Singly Occupied Molecular Orbital), not HOMO. Now assume that you have two SOMOs (or SOMO and SOMO-1 if you prefer). Here are my suggestions: The first thing ...
• 806
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### When orbitals are labeled based on their irreps in D2h, how are the orbitals ordered for an N atom?

"Nitrogen atom has a point group of Dinfh, but ⁠CFOUR uses a lower symmetry of D2h instead" The point group of the N atom (or any atom) is $K_h$, not $D_{\infty_h}$, the latter would be ...

### Most up to date explanation explaining the stability of high spin multiplicity (multiplicity=2S+1 ) states?

The paragraph on Wikipedia you are citing reads in full Two different physical explanations have been given[5] for the increased stability of high multiplicity states. In the early days of quantum ...
• 19.7k

### In which irreducible representations shall I put the electrons in an F atom in PySCF?

If for oxygen you have: {'A1g': (2,2), 'E1ux': (1,0), 'E1uy': (1,0),'A1u': (1,1)} Then for fluorine I would simply put one more electron in either of ...

### How to get the HOMO/LUMO from spin up/down eigenvalues?

If you want to have eigenvalues for each spin, you need to run a spin polarized calculations. This will set the program to treat both spins differently. After that, you could obtain different values ...
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### Is it possible to plot the pDOS or visualize the molecular orbitals from GAMESS outputs?

Yes, you can get what you want. If you have a Gaussian .fch file, you can visualize MOs using GaussView/Multiwfn/... any GUI you like. And you can plot PDOS by loading the .fch file in Multiwfn(http://...
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### How do I determine the charge and spin multiplicity of a system?

My answer to "How to select charge and multiplicity for macro-molecules?" explains how to find the charge and multiplicity of a system. The reason why you cannot just figure it out based on ...

### Numerical atomic orbitals vs Gaussian-type orbitals for molecular calculations

In some cases at least, NAO give smaller BSSE (basis set superposition error). Here is the figure from the FHI-aims paper: The BSSE here is the difference between red and black lines. It is small, ...
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1 vote

### Is there a way to add 4f-oribital information in Pseudopotential?

You can try the PP: Eu.pbe-spdfn-kjpaw_psl.1.0.0.UPF. I have used this one for Hubbard correction of Eu-4f orbitals a while back. I have uploaded it here: https://drive.google.com/file/d/...
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1 vote

### How may I calculate atomic orbital energies using VASP?

I will suppose that you have done the following as your approach looks correct, you shoud have performed an (SCF) calculation and include a sufficient number of bands to accurately capture the d ...
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1 vote

### How to get the crystal/ligand field splitting of d orbital of Fe complex using Quantum Espresso

You should take into account that for this type of square planar complex the set of 5 "d" orbilals of the iron atom are the ones that must be considered for the calculation. Usually, ...
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1 vote

### How do I interpret the Gaussian16 wavefunction file?

https://aim.tkgristmill.com/wfxformat.html WFX format specification. WFX is an AIM file. Yes, Cartesian. https://wordpress.nmsu.edu/tmanz/files/2020/06/WFX_file_programmers_guide_06_14_2020.pdf WFX ...
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