Questions tagged [gaussian]

For questions related to the Gaussian electronic structure program

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5
votes
1answer
163 views

Calculated Redoxpotential is too far away from experimental value

I calculated the redox potential with Gaussian for hydroquinone with different combinations of functional/basis sets always values like 5.4V (B3LYP/6-311G+(2d,p) and SMD model). The experimental value ...
5
votes
1answer
42 views

How to alter the charge and multiplicity of a molecule in Gaussian?

I want to perform redox potential calculations using the Gaussian. To check if I'm setting things up correctly, I want to compare it to a benchmark database published by Grimme et al.[1] I performed ...
7
votes
1answer
71 views

Symmetry group of p-benzoquinone

I am trying to calculate the UV-visible spectrum of p-benzoquinone. In the literature, the point group of p-benzoquinone is $D_{2h}$, but when I optimize this molecule in the ground state with ...
6
votes
1answer
38 views

Transforming basis functions from Cartesian to speherical

I read the basis set from book A d-type GTO written in terms of the spherical functions has five components (Y2,2, Y2,1, Y2,0, Y2,1, Y2,2),but there appear to be six components in the Cartesian ...
5
votes
2answers
140 views

The format and values provided by Basis Set Exchange

In this question and answers, I found that Basis Set Exchange provides information about the orbitals (e.g., the orbital exponents and contraction coefficients). For example, the following example is ...
10
votes
4answers
666 views

How can I find the parameters in a basis set?

I have a question about the basis functions of Gaussian. When the basis function is set (e.g., 6-31G), I would like to know the specific value of Gaussian's parameters for each atom. In particular, I ...
10
votes
2answers
217 views

Calculating the excited state dipole moment

I am trying to calculate the dipole moment of an excited state, using "Gaussian" software. My input commands were: ...
7
votes
2answers
148 views

Does QC convergence mode in Gaussian make a difference?

I have been using Gaussian16 por metal complexes SCF single-point calculations involving triplets to investigate phosphorescence. I have actually run into trouble (very long computational time, even ...
7
votes
1answer
55 views

Frequency error in Gaussian CASSCF(10,10)

I am stuck in calculating the frequencies of one optimised geometry for naphthalene CASSCF(10,10) with Gaussian 16. I have optimised its geometry and checked the active space is the pi system of it, ...
4
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0answers
61 views

Gaussian warning [closed]

I am running an ONIOM optimization calculation on GAUSSIAN software and when I open the LOG file I get a warnig saying: ...
7
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2answers
293 views

Geometry optimization with Moller-Plesset MP4

Can we optimize a molecular structure using Moller-Plesset MP4 method on GAUSSIAN software? If yes what keyword do we have to add?
10
votes
0answers
161 views

How to plot a Gaussian cube file with python/matplotlib? [closed]

I know there are programs that can automatically visualize .cube files (like VMD), but I'm trying to do it myself in python/matplotlib (or equivalent) to better understand what the numbers mean. I ...
9
votes
1answer
108 views

How to eliminate imaginary frequencies during a Gaussian geometry optimization?

When conducting a minimization on Gaussian software, What are the procedures used to eliminate imaginary frequencies if we have already found a stationary point? Are there any keywords that would help ...
8
votes
1answer
156 views

How to generate a input file for gaussian in Avogadro 2? [duplicate]

I made auto optimization working by installing openbabel using sudo apt install openbabel. Is there any way to make Gaussian extension working by doing something? I'...
11
votes
3answers
206 views

Quantum chemistry in external electrostatic field?

Which quantum chemistry methods can be used in an external electrostatic field? Also which software supports that? I'm interested in anything from semiempirical (eg XTB) to DFT (eg ωB97, B3LYP-D3) ...
8
votes
0answers
59 views

Visualizing wavefunctions in real space [closed]

I would like to generate wavefunctions as functions of spatial coordinates (X, Y, Z) using Gaussian G09 and then visualize them. How might I go about doing this? I am using Linux and my preferred ...
8
votes
0answers
84 views

How to compare the stability of two nano-structures using ab-inito calculations? [closed]

I have recently started working on Double Perovskites Quantum Dots and one of the main issue with them is that they are not much stable. Some papers did talk about how much stable there compounds are ...
6
votes
0answers
71 views

How to calculate energy gradient and Hessian with respect to only a few internal coordinates using Gaussian? [closed]

I would like to form the (numerical) gradient and the Hessian of the total electronic energy with respect only to a few internal coordinates (namely, the six intermolecular coordinates of a weakly ...
5
votes
0answers
73 views

How to extract Cartesian gradient with more digits than 8 using Gaussian? [closed]

I would like to obtain the Cartesian gradient from a Gaussian formatted checkpoint file with more digits than 8 (specified in scientific notation). Is there any way to do this?
6
votes
1answer
328 views

Can a file in the Gaussian CUBE format be voxelized?

My aim is to voxelize a CHGCAR file. I am trying to build up a workflow to do the same. With the aid of the Matter Modeling community members, I have figured out a way to convert a CHGCAR file into ...
8
votes
2answers
308 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 $2p_x$, ...
9
votes
2answers
118 views

Is it possible to do a Gaussian redundant scan with some fixed bonds?

I'm trying to do a redundant PES scan of a hydrogen abstraction in a Gaussian job while maintaining the rest of the system fixed. I need to scan the coordinate where H5 approaches to H6, maintaining ...
5
votes
2answers
82 views

How to use fractional numbers as arguments for keywords in Gaussian input?

I have used both Gaussian09 and Gaussian16 and one thing that seemed unusual to me is that I was unable to enter any fractional number as one of the arguments for a keyword in the Gaussian input file. ...
5
votes
1answer
416 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 ...
11
votes
1answer
274 views

Why does Gaussian ignore the opt=maxcycles keyword for optimizations?

I have been using both Gaussian09 and Gaussian16 recently to optimize some metal complexes. The Gaussian manual (for both versions) indicates that the maximum number of steps in a geometry ...
11
votes
1answer
298 views

What units are used in Gaussian 16 for dipole derivatives output?

I ran a frequency analysis employing Gaussian 16 on MP2/6-31+G(d,p) level of theory with the keyword iop(7/33=1) in order to have access to dipole derivatives with ...
8
votes
1answer
73 views

Calculation of dispersion energies for organometallic complexes with Gaussian

I've tried to calculate dispersion energies of some organometallic complexes with the Gaussian software using WB97XD/Gen (...
10
votes
1answer
233 views

How to calculate the band structure of a protein molecule

I want to calculate the band structure of a protein molecule. How can I do it using Siesta of Gaussian? I am thinking about QE/VASP as the number of atoms are 600 and computationally it is not ...
8
votes
1answer
189 views

Problem obtaining a Raman spectra of a graphene structure

I am trying to obtain the Raman spectra of a graphene structure using Gaussian. I used the input below, but when I did it, I got this error: ...
7
votes
1answer
78 views

What does "Test job not archived" mean?

I am running frequency computation with geom=connectivity in Gaussian. It all converges now but at the very end of the last convergence it says: ...
6
votes
1answer
135 views

Gaussian: Transition state convergence question

I am running a TS computation in Gaussian 16. It performs several steps. At the end of each there is a summary on whether Maximum Force, ...
10
votes
1answer
130 views

How to generate accurate displacements along normal modes?

How can i displace my structure along a particular normal mode, without coupling to other modes ? Rather than a exact mathematical procedure, I am more interested in a software/script/package that can ...
11
votes
3answers
252 views

CCSD and CISD size-consistency problem

I have performed a Gaussian16 calculation to explore the size-consistency problem for the CISD method. The system I am studying is the water dimer and the results are not what I expected at first. I ...
7
votes
1answer
60 views

PES of Tetramethylthiuramdisulfid / Problem with Disulfidbridge

I like to perform a DFT Study on Tetramethylthiuramdisulfid. So I made a structure optimization for my start structur with PW6B95D3/aug-cc-pvtz to get a good structure to begin my dihedral scan to get ...
32
votes
5answers
3k views

What is a good replacement for Gaussian?

When I started studying computational chemistry (circa 2007), my supervisor used to tell me about the controversy surrounding Gaussian, Inc. regarding the banning of researchers involved in the ...
11
votes
1answer
162 views

Using "soft" constraints / bias in geometry optimization?

I study molecules weakly bound to nanoclusters and surfaces. During geometry optimization, I often run into problems like for example a small metal cluster behave nicely and has a given, stable ...
6
votes
0answers
90 views

Two-stage unbinding & binding energies with DFT

I'm trying to calculate the stability of the product of a coordinate bonding process of molecules A and B in the polarizable continuum solvent model (PCM, solvent set to water). I'm getting energies ...
5
votes
0answers
124 views

How can I calculate and plot the molecular orbitals (MO's) from the Gaussian wavefunction file? [closed]

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
95 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 : ...
6
votes
3answers
199 views

Units of energy in Gaussian

I want to calculate the redox potential for a molecule in water using Gaussian. I found a tutorial at 1, but I'm got confused about the units at the end. They have a result for the Gibbs Free Energy ...
10
votes
1answer
181 views

A concern about IRC results

I've run an IRC (intrinsic reaction coordinates) calculation from my TS (transition state) and got two minima for each side. I am concerned about them. One of them took about 100 steps to be achieved ...
10
votes
2answers
365 views

How to perform charge analysis for a molecule

I am doing dehydrogenation of a molecule (say $\ce{C12H12}$) and I want to do charge analysis for dehydrogenated system ($\ce{C6H6}$). How I can proceed? I can use Quantum ESPRESSO and Gaussian ...
10
votes
1answer
92 views

Calculate Redox Potential

I am interested in calculating some redox potentials of organic compounds (H,C,N,O,F,Cl,Br) in organic solvents such as MeCN. I do not need absolute agreement with experiments since this is just a ...
8
votes
1answer
47 views

Simulation of electronic potential from nanoparticles interacting with molecules

I work with SERS, where the Raman signal gets enhanced by the electric field of the nanoparticles. Now I like to simulate this kind of spectrum with Gaussian. I found a paper[1], where it looks very ...
9
votes
1answer
185 views

A good software for DFT optimization and nonlinear optical properties

I'm running a series of calculation for nonlinear chromophores. The general pipeline is geometry optimization (B3LYP/def2-TZVP) -> Frequencies -> Hyperpolarizability calculation (M06-2X (or CAM-...
9
votes
3answers
923 views

Which software is good with generally contracted basis sets?

Recently, I learnt that basis sets can be contracted as segmented (like def2 or 6-31G) or general (like cc-PVTZ, or ANO). The general contraction allows all the primitives to appear in all shells, ...
8
votes
0answers
346 views

How to interpret second order perturbation theory analysis from NBO calculations? [closed]

The question is quite simple — how to interpret NBO results of second order perturbation theory analysis? As I have read several papers the most important interactions are $\pi\rightarrow\pi^{*}$, $LP\...
9
votes
1answer
3k views

How to fix Error Link9999 in Gaussian

I have a problem with geometry optimization in Gaussian software with M062X method. The structure was smoothly optimized using M062X/Gen. Nevertheless, I need very accurate results so afterwards the ...
9
votes
1answer
441 views

Is it possible to do TD-DFT/6-31G+(d,p) calculations on a laptop?

In the recent publication: "Density Functional Theory Calculation on the Structural, Electronic, and Optical Properties of Fluorene-Based Azo Compounds", the author claimed to have used ...
10
votes
4answers
876 views

Codes for post-processing Gaussian cube files?

I have generated MOs of a molecular system and I need to recreate its electronic density via $\rho(r)=\sum_{A_i}|\psi_i(\mathbf{r})|^2$ where $A$ is a set of occupied MOs. I am trying to do this via ...