# Questions tagged [wavefunctions]

Refers to a mathematical description of a quantum state of a system.

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8 votes
2 answers
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### How do I interpret the Gaussian16 wavefunction file?

I'm new to gaussian16. The wave function file that I obtain as a result of the "Energy" calculation. It consists of five distinct parts : PART 1 : ...
2 votes
1 answer
96 views

### Understanding the complexity of geminal-based wavefunctions

Cross-posted on Reddit. I have been reading through [1] to get a better understanding of geminal-based methods. Some short passages are included below: The occupation of each orbital in the expansion ...
3 votes
0 answers
177 views

### Understanding derivation of geminal based methods [closed]

Cross-posted on Reddit. I have been reading through [1] to get a better understanding of geminal based methods. This is one of two questions that I'm asking about that paper on this site, the other ...
2 votes
0 answers
101 views

### |psi|^2 calculation (1D) for diamond structure silicon not showing full dataset for all bands: Quantum ESPRESSO

Dear Quantum ESPRESSO users, I was trying to calculate the |psi|^2 calculation (1D) for diamond structure silicon at a single kpoint (gamma point). I have used the semicore pseudopotential that ...
1 vote
0 answers
50 views

### Question on known expression (see post) of exact XC functional in analytic (but not closed) form [closed]

This paper analytically solves the "inverse DFT problem" of mapping the ground-state density to the exact XC functional. And the exact density, i.e. the FCC/FCI density, can be expressed as ...
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 ...
6 votes
0 answers
108 views

### Basic but fundamental question on the extended Koopman theorem using Dyson orbitals [closed]

Let there be some ground-state N-electron species named A. A Dyson orbital for Q is defined as the overlap between Q and (Q with one electron removed). The extended Koopmans theorem now states that ...
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 ...
3 votes
1 answer
49 views

### Are frozen-core approximations for the elements of first or second row accurate for potentially extremely short bond distances present in the molecule

Yes, it is about my molecule that you've heard of (but never seen) in my previous questions. The molecule, which contains only C, Al, B, Cl, Mg, N, O, S and Si, is macromolecular with quite crowded ...
6 votes
3 answers
382 views

### SIESTA output wavefunctions: all vs selected?

Using SIESTA, I want to plot the wavefunctions around the Fermi level (similar to HOMO/LUMO). Also, I want to do COOP analysis. From the SIESTA manual, I can setup to write the wavefunctions ...
4 votes
0 answers
73 views

### Do the orbital energies of ground-state Dyson orbitals exactly capture arbitrary excitation energies and/or ionisation potentials/electron affinities?

According to an answer to my question on whether the Kohn-Sham orbital energies theoretically exactly capture arbitrary ionisation potentials and/or excitation energies, the answer is no for both ...
3 votes
1 answer
154 views

11 votes
1 answer
304 views

### How to use wavefunctions/density to determine which orbitals lead to edge states?

I have a large matrix for a 1D zigzag edge model of an otherwise $3\times 3$ tight-binding Hamiltonian (3 basis functions, each corresponding to an atomic orbital), involving the variable $k_x$. The ...
12 votes
1 answer
310 views

### How to numerically solve real-space 1D time-independent Schrodinger equation using 2D momentum-space Hamiltonian?

Consider the usual simple 2-level graphene Hamiltonian with mass in momentum-space where: $$H(k,V)=-t \sum_{\delta} [\cos(k\cdot\delta)\sigma_x-\sin(k\cdot\delta)\sigma_y+V\sigma_z],$$ where $t$ is ...
16 votes
1 answer
2k views

### Does the Schrödinger equation have unique solutions?

I am learning DFT and the Hohenberg Kohn Theorem of Existence. It says that there is a one-to-one correspondence between the external potential and the density. However the proofs that I have seen ...