Questions tagged [orbitals]

For questions about properties and types of orbitals

Filter by
Sorted by
Tagged with
5
votes
1answer
77 views

Modify ORCA orbitals for CASSCF

I have run a HF calculation on naphthalene and I have checked the MOs that have been obtained. Now, I have to select my active and inactive orbitals for CASCF(10,10). As there are 34 occupied orbitals,...
6
votes
0answers
26 views

Confused by NBO output, due to missing bonds

I'm about to do an NBO analysis to evaluate bond characteristics in a novel transition-metal complex. As I have never done anything like that, I tried to understand the basic output for an octahedral ...
10
votes
1answer
85 views

Orthonormality of Kohn-Sham orbitals

I was wondering if Kohn-Sham orbitals corresponding to a different Bloch wavevector should be orthogonal? I know that we should have $$\int d \boldsymbol{r}\phi_i(\boldsymbol{r}) \phi_j^*(\boldsymbol{...
6
votes
0answers
50 views

Orbital space clustering

I am interested in how the orbital space of a system can be partitioned into clusters. I read reading 'Cluster many-body expansion: A many-body expansion of the electron correlation energy about a ...
8
votes
1answer
111 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 ...
5
votes
0answers
67 views

Predict the density of states (DOS) diagram for rhenium oxide (ReO3) from the molecular orbital diagram

Yesterday I made this query on Chemistry Stack Exchange, and a user has felt that perhaps here I will get a quicker answer. The structure of rhenium(VI) oxide, $\ce{ReO3}$, is similar to that of ...
8
votes
2answers
269 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 $2p_x$, ...
11
votes
2answers
194 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 ...
13
votes
1answer
241 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
80 views

Is there a software package to analyse interactions in crystals? [closed]

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
41 views

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

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
275 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, $M = {(\ce{O}, R_\ce{O}), (\ce{H}, R_\ce{H}), (\ce{H}, R_\ce{H})}$, ...
14
votes
1answer
363 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 ...
5
votes
0answers
104 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
83 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
197 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
163 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
131 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
105 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
92 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
122 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
187 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
700 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?