Questions tagged [gaussian]

For questions related to the Gaussian electronic structure program

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4 votes
0 answers
59 views

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 ...
2 votes
1 answer
44 views

'The combination of multiplicity electrons is impossible' in Gaussian

I am trying to calculate the energies of the S1 and T1 states of a molecule with UDFT using Gaussian. For the T1 state, I can successfully use the following input file: ...
4 votes
0 answers
50 views

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 ...
5 votes
1 answer
136 views

What is the problem in my gaussian input?

I want to obtain the single point energy of a Ni-complex molecule, with a mixed basis set using the Gen keyword. The input is: ...
2 votes
0 answers
18 views

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 ...
4 votes
0 answers
48 views

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 ...
0 votes
0 answers
43 views

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 ...
1 vote
0 answers
19 views

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 ...
5 votes
2 answers
100 views

Trying to get concurrent results for a TDDFT calculation in Gaussian and ORCA

I am trying to do a simple TDDFT calculation in both Gaussian and ORCA from the exact same reference Geometry. I am using the same functional (making sure to use ...
2 votes
0 answers
44 views

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? ...
8 votes
1 answer
675 views

Restart potential energy scan in Gaussian with additional scan points

I have finished a scan of a bond length, but I need to continue the coordinate scan adding more points to the same scan. I thought of writing a second input file from the last geometry, relaunching ...
2 votes
0 answers
14 views

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 ...
3 votes
1 answer
136 views

Singlet excited state optimization gaussian issue

I hope someone here can help me with some TD-DFT calculations. I am trying to calculate the excited state optimised structures and energies of some Germanium compounds. Firstly, I run a TD calculation ...
5 votes
2 answers
214 views

Gaussian 16: Relaxed scan using Jacobi coordinates expressed using generalized internal coordinates

For teaching porpouses, I would like to make a relaxed scan for an A-BC system (for example, the isomerization of of H-NC to H-CN or CH3-NC to CH3-CN) with Gaussian 16 using generalized internal ...
3 votes
1 answer
122 views

Difference in energy between first excited singlet and first excited triplet with DFT in Gaussian

I want to ask a further question related to this one. I have performed the calculations as explained and obtained a difference in energy of 0.71eV with the TDA-DFT level of theory. Then, I tried to do ...
4 votes
1 answer
113 views

Methologies to calculate excited states in Gaussian

Referring to previous questions asked here, I would like to pose a more general question about the calculation of ΔE(S1-T1) for organic molecules with the software Gaussian16. In particular, I have ...
5 votes
1 answer
145 views

S1-T1 energy difference in Gaussian

I would like to calculate the energy difference between the first excited singlet and the first excited triplet of a given molecule in solvent, on Gaussian. In this publication, they state that using ...
1 vote
2 answers
77 views

GAUSSIAN 16 Error with CCSD(T)

My input file is: ...
3 votes
0 answers
29 views

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 ...
4 votes
1 answer
48 views

Is it possible to find H-bond enrgy with O-H distance less than 0.95A?

I am trying to calculate the energy of a hydrogen bond between RCOO- and Tyrosine (figure below). I freeze the O-O bond at 2.8A and calculate the energy by changing the distance between O-H. But when ...
5 votes
1 answer
59 views

Is it possible to predict reduction reaction products with a Gaussian program?

In a molecular geometry calculation using a Gaussian program, can I see changes in bond lengths or changes in structure when one electron enters the molecule through a reduction reaction? for example, ...
3 votes
0 answers
107 views

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 ...
8 votes
2 answers
2k views

Emission and absorption UV-Visible spectrum using GAUSSIAN-09

I am currently studying the UV-visible spectrum of ethylene using GAUSSIAN-09. I optimized the ground state(# opt b3lyp/6-31g geom=connectivity) then used the ...
3 votes
0 answers
83 views

Error in output in gaussian [closed]

I am beginner regarding the use of Gaussian. Currently, i am trying to study the vibration of HgCl2. I have an error: Error termination via Lnk1e in /nfs/opt/Gaussian/16.c01/avx2/l301.exe Any help is ...
8 votes
0 answers
103 views

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 ...
7 votes
1 answer
103 views

How many non-redundant internal coordinates are needed for optimisation of linear molecule?

I have been working to implement optimisation in internal coordinates (for a transition state search software I am working on). However, the implementation details are almost always glossed over in ...
5 votes
1 answer
170 views

How is the dipole moment defined in Gaussian?

I wonder if the origin of the permanent dipole moment calculated by Gaussian (16) is always the center of mass (0,0,0 if "Nosymm is used)? For the neutral molecule it does not matter, but I am ...
2 votes
0 answers
40 views

how to calculate the total charge for a specific fragment in a molecule using NBO analysis with Gaussian? [closed]

hi my molecule is devided into 5 fragment, I want to perform an NBO analysis and calculate the total charge of each fragment instead of doing it by hand (by summing atomic charges) , is there a way to ...
2 votes
0 answers
45 views

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 ...
3 votes
1 answer
185 views

Comparison between the ordering of Molecular Orbital coefficients between Gaussian and PySCF

I am trying to compare the Molecular Orbital coefficients obtained from PySCF and G09 program. Below is the PySCF and Gaussian input and output. I am using 3-21G basis and RHF method for both the ...
3 votes
1 answer
103 views

How is the LUMO lower energy than the HOMO for triplet state restricted-open shell DFT calculation?

I recently ran a calculation using the ROB3LYP/LANL2DZ level of theory for a triplet spin molecule. While analyzing the results, the HOMO is doubly degenerate and the LUMO is singly degenerate. I ...
2 votes
0 answers
60 views

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 ...
3 votes
1 answer
257 views

Advice on converging a restricted open-shell DFT (rob3lyp/LANL2DZ) single point Gaussian09 calculation for a triplet spin-state molecule?

I am running a single point calculation on a fragment of a molecule using restricted open-shell theory. The fragment is in the triplet spin-state and of pentagonal planar structure (D5h). I ran the ...
1 vote
0 answers
67 views

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: ...
3 votes
0 answers
61 views

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 ...
5 votes
1 answer
75 views

Using Hindered Rotor Scans With Different Convergence Criteria from Gaussian

I am having trouble with a difficult convergence in Gaussian16. I am running two separate PES scans for hindered rotors in my molecule that will eventually be used in subsequent rate calculations. I ...
4 votes
2 answers
102 views

Cannot optimize hexa aqua Cu(II) and Fe(III)

I try to optimize very simple systems - hexa aqua Cu(II) and hexa aqua Fe(III) - in Gaussian 16. The inputs are provided in the end of the post. Unfortunately, the geometry optimization never finishes ...
2 votes
1 answer
89 views

using the gen function in gaussian

I'm trying to optimize a structure that contains Pd atom with the gen function on gaussian16 ...
4 votes
1 answer
298 views

Frequency run does not converge in Gaussian16

I have been optimizing some particularly tricky structures with Gaussian. The optimizations end well and they don't have negative frequencies. However, when checking the convergence of the frequency ...
8 votes
2 answers
610 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 : ...
5 votes
1 answer
277 views

Convergence problem in geometry optimization in Gaussian16

I have a quite big set of molecules to optimize and study and, after some research in the literature, I selected B3LYP/6-311G* level of theory. These molecules are quite big and wobbly, so I expected ...
10 votes
1 answer
534 views

How can I specify different theory levels for different atoms in Gaussian?

I have a bunch of geometry optimisations I want to run for a cation Metal-organic complex. This is going to be a repeat of calculations that were done in "Turbomole" previously and my Prof. ...
6 votes
3 answers
237 views

Frozen core Stability Calculations in G09?

I am trying to calculate the stability of CO at HF/3-21g level using G09. I am trying to reproduce an issue that was observed in PySCF, and I have made the following observations: If I use the ...
3 votes
1 answer
104 views

How do you make sure the reaction is diffusion limited (Gaussian)?

I am investigating the mechanism of hydrogen transfer between a hydroperoxyl radical and an aromatic hydroxyl group donating it. The problem is that I cannot find transition state structure. So far, I'...
6 votes
3 answers
600 views

How to run multiple Gaussian jobs one after another in Linux

I want to run multiple Gaussian jobs (one after one). I have a folder which contains more than 30 molecules and I want my calculation to start with molecule 1 then when the job is finished, start the ...
2 votes
0 answers
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 ...
4 votes
0 answers
53 views

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 ...
4 votes
0 answers
47 views

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 ...
1 vote
0 answers
108 views

Gaussian does not reproduce UV-Vis spectrum [closed]

I am performing some TD-DFT calculations to reproduce the UV-Vis spectrum of a molecule using Gaussian. After optimizing the structure, I performed a TD-DFT calculation with 150 states and I tried ...
4 votes
1 answer
172 views

Computing the kinetic energy of a molecular orbital

I want to compute the kinetic energy of the molecular orbitals computed by Gaussian 09, the variable U in this paper. Can it be computed from the orbital energy using a formula or does it need to be ...