Questions tagged [orbitals]

For questions about properties and types of orbitals

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8
votes
1answer
162 views

How to calculate and plot localised orbitals with xTB?

The question is similar to How to calculate/plot molecular orbitals with XTB? Hence we can produce molden files from xTB calculations, which include the molecular orbitals. How do I proceed to get ...
6
votes
0answers
69 views

Is there a software package to analyse interactions in crystals?

I have been using Quantum ESPRESSO, specifically the pp.x module to study interactions via charge density plots. The process is slow as for crystals containing ...
5
votes
0answers
32 views

Kinetic energy cut-off for Gaussian-type orbitals when applying periodic boundary conditions

I have a solid with PBC (periodic boundary conditions) and I want to perform a DFT simulation. I use GTO as the basis. In a paper I read, I can transform the GTO to a Bloch function (crystalline ...
9
votes
1answer
209 views

How can I implement the Cartesian harmonics?

I'm studying the quantum chemistry calculation and now trying to implement the basic methods. For example, given a water molecule, $M = {(\ce{O}, R_\ce{O}), (\ce{H}, R_\ce{H}), (\ce{H}, R_\ce{H})}$, ...
13
votes
1answer
187 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 ...
4
votes
0answers
46 views

How can I calculate and plot the Molecular orbitals (MO's) from the Gaussian wavefunction file?

This a follow-up question to my previous question. And as per the answer one could create M.O orbitals from the primitives. As a new user of Gaussian, is there any method (or algorithm) to followed so ...
7
votes
1answer
68 views

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 : ...
8
votes
1answer
109 views

How to get the .47 file from ORCA for natural bonding orbital analysis

I am trying to perform NBO analysis with relaxed density matrix with the open-source program JANPA. I am following the guide here. The first step is to get the NBO input .47 file from Orca v4.2.1. The ...
9
votes
1answer
154 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, ...
7
votes
1answer
108 views

How to calculate/plot molecular orbitals with XTB?

I started playing with the XTB program (XTB is developed by Prof. Grimme group's, is based on tight binding and uses the GFN force field). Question: How can I calculate/plot the molecular orbitals? I ...
11
votes
1answer
88 views

Is there any relation between static correlation and finite-temperature smearing?

I am new to this field, so there is a chance that I am mixing two entirely different concepts together, but it seems to be that static correlation and finite-temperature smearing in DFT are somehow ...
6
votes
0answers
61 views

Unresolvable inconsistency between charge and multiplicity and orbital occupancies. Error while Distance Scan [closed]

I get the message mentioned in the title after a distance scan with a Gaussian calculation. I have bound a gold atom to a carbon in the pyridine ring and now pull this further and further out with a ...
15
votes
2answers
100 views

What is the difference between orbital localisation and NBO?

I am new to computational chemistry, I have used mainly GAMESS and Orca. In GAMESS, there are orbital localisation schemes like Pipek-Mezey, Ruedenberg-Edminston, etc. which generate orbitals that ...
10
votes
1answer
160 views

How to interpret molden AO/MO coefficients?

A simple calculation with Molpro 2012 on H2 molecule in cc-pvtz basis produces a molden file with 28 molecular orbitals. Each MO is defined with 30 AO/MO coefficient, but the number of symmetric AOs ...
11
votes
5answers
590 views

Plotting of natural bond orbitals (NBOs)

Which quantum chemistry programs can compute natural bond orbitals (NBOs)? Which visualisation tools can I use subsequently to plot pictures of the NBOs?