Questions tagged [gaussian]

For questions related to the Gaussian electronic structure program

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How does the line search in geometry optimisations work?

I am trying to write a Newton-Raphson geometry optimisation script in python (Current version of my code) using the energy, gradient and Hessian from Gaussian 16. In order to reach a minimum, I would ...
evd's user avatar
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4 votes
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Calculation of S1 energy in Gaussian

I am trying to calculate the energy of the S1 state with UDFT in Gaussian software. I understand that, generally, one should manipulate the charge and spin multiplicity to manually change the ...
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Computational chemistry

Can I use Google Collab to run my Gaussian calculations? Due to the lower specification of my system, I can not run my calculations. I have to generate .wfn file. Is there any other idea or ...
Inorganic Chemistry's user avatar
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Struggling with Mixed Basis Set Inclusion for IRC Calculations

I'm trying to compute the IRC for a W complex, and I'm using Def2TZVP for W and 6-311G** for the rest of the atoms. However, when I include the mixed basis set, Gaussian 16 generates a syntax error. I ...
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How to compute only part of molecular Hessian accurately (hybrid Hessian or partial Hessian calculation)?

Hessian is required for minimisation and transition state (TS) optimisation algorithms. While the full Hessian at a certain level of theory is calculated usually for TS optimisation, usually ...
S R Maiti's user avatar
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How to calculate charge transfer (CT) in NBO Analysis using Gaussian 09?

I have a coronene structure, functionalized with hydroxyl groups. I want to calculate the charge transfer (CT) between the coronene and the hydroxyl group, using NBO analysis as implemented in ...
Bruno's user avatar
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3 votes
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Constrained geometry optmization: Molecule interacts with its surroundings

I have a water cluster(suppose) generated from MD run. Now, I want to optimize the geometry of only one water molecule of interest using QC methods (e.g. B3LYP/6-31+G(d,p)). I intend that the water ...
Pro's user avatar
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Advise in generating ESP surfaces from Gaussian .cube files using the IQmol software

I am trying to generate an ESP surface of a Gaussian09 calculation using the iqmol software. I have used Gaussview to visualize the ESP surface by generating .cube files from .fchk files (using the ...
Kevin Freddo's user avatar
3 votes
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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 ...
Kevin Freddo's user avatar
2 votes
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Are there any good tutorials on SHARC-Gaussian interface?

I am an aspiring quantum chemist planning on trying out the SHARC approach to study excited state proton transfer dynamics of organic molecules. I am comfortable with Gaussian 16 as that is the ...
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Frequency calculation using Quantum Espresso

I want to calculate the frequency using quantum espresso. How can I get the input file of frequency calculation using QE? ...
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Can I define molecular units on NBO3.1 or NBO6.0?

I'm studying donor-acceptor charge transfer (CT) process between tetrakis(m2-acetato)-di-Wolframium (acceptor) with an acetonitrile (donor) at the B3LYP-D3BJ/def2-TZVPD level of theory. The W···N ...
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How much should you shift fragment energies to create an energy level diagram?

I am creating an energy level diagram for the orbitals of [XeF₅] - molecule produced by two fragments: [Xe] 4+ and [F₅] 5-. There is a very large energy difference between the two fragments, so I ...
Kevin Freddo's user avatar
2 votes
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Help setting the input geometry into standard orientation for a single point g09 calculation

I am trying to run a single point g09 calculation for a pentagonal planar molecule with D5h symmetry using the B3LYP/LANL2DZ level or theory. I would like the calculation to use symmetry, however the ...
Kevin Freddo's user avatar
2 votes
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29 views

What is the procedure to calculate the vibrationally resolved UV-Vis spectrum in solvent with Gaussian?

I followed the tutorial reported here to calculate the vibrational resolved spectrum in vacuum. The spectrum seems ok and it is actually close to the experimental one. However, I would like to add the ...
Laura's user avatar
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1 vote
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How to seperate structures in bulk with connectivity from a relaxed scan in Gaussian 16?

I aim is to construct the PES for a molecule considering a specific bond length as the scan coordinate. I am using the Relaxed-Scan feature of Gaussian 16 for this using the ...
Uranium238's user avatar
1 vote
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Fluorescence solvated band shape in Gaussian16

I am trying to calculate the fluorescence spectra in solvent with Gaussian16. I followed the example reported here to calculate the value of the vertical emission. However, in the same link, I read: ...
Laura's user avatar
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Why is this geometry optimization in Gaussian not working for a system containing an amino acid, a water molecule and a metal (Pb) ion?

I started optimising a system containing amino acid residue, water molecule and a toxic metal ion, in proving a supposed reaction steps that might take place in inhibiting enzyme activity. The ...
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