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Questions tagged [gaussian]

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5 answers
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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 ...
1__'s user avatar
  • 513
19 votes
1 answer
533 views

Retrieving Translational and Rotational Modes

I'm doing some post-processing using the vibrational modes of a molecule to solve a linear system of equations, but I believe I need all the modes in order to have a single, well-determined solution. ...
Tyberius's user avatar
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18 votes
1 answer
188 views

Discrepancy between numerical and transformed derivatives

This is related to a prior question of mine Derivatives with respect to user defined vibrational modes. While that one focuses on potential software to use for derivatives with respect to normal modes,...
Tyberius's user avatar
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16 votes
1 answer
840 views

How to map the electrostatic potential from GAUSSIAN, on a solvent accessible surface?

Gaussian cubegen and surface generators in Gaussview seem to only allow to map the ESP on SCF densities. I used G16 for the ESP generation. I would like to plot it on the solvent accessible surface. ...
DSVA's user avatar
  • 363
15 votes
2 answers
887 views

What are the parameters that need to be calculated to design the structure of a molecule?

Before performing Molecular Dynamics on a co-polymer that doesn't have a ready-to-use structure anywhere, the monomer fragment was built in Avogadro software with 0 net charge, B3LYP theory and 6-31G(...
Kavya Mrudula's user avatar
15 votes
1 answer
3k 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 ...
S R Maiti's user avatar
  • 7,011
15 votes
1 answer
1k views

CCSD(T) Transition State and Ground State Calculations in Gaussian09: "Unable to Determine Lambda"?

I’m doing CCSD(T) calculations (for both transition and ground state geometries) on a series of small molecules in Gaussian09. Several similar calculations terminated without any problems but one TS ...
QuantumX's user avatar
  • 467
15 votes
1 answer
338 views

What are good basis sets and functionals for Ni, Cd and Pb?

I will setup a single point energy calculation using Gaussian for a system containing atoms of B-N-Ni, B-N-Pb and B-N-Cd. The system are slabs of boron-nitride [1,2] interacting with those metals. ...
Camps's user avatar
  • 23.6k
14 votes
2 answers
1k views

A CCSD(T) geometry optimization in Gaussian09 is deviating too far from the minimum. How do I deal with it?

I am doing a CCSD(T) geometry optimization on a series of molecules. One of the geometry optimizations took about 2 weeks even though an analogous molecule with the same number of basis functions took ...
QuantumX's user avatar
  • 467
14 votes
1 answer
14k 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 ...
user avatar
14 votes
1 answer
217 views

What is the precise location of the grid points/voxels in a Gaussian .cube file?

Assume that we have a cube file that contains Ni * Nj * Nk points, and an origin at 0, 0, 0, where are the data points actually ...
Anubhab Haldar's user avatar
14 votes
1 answer
2k views

How to calculate sigma-profile using COSMO/RS and Gaussian 16?

Gaussian 16 claims to have an external tool to calculate sigma-profile COSMO/RS (Klamt) [1]. In the support website, there is a SCRF flag for COSMORS [2]. How do I calculate sigma-profile using ...
Protima Rani Paul's user avatar
13 votes
1 answer
703 views

What is the meaning of periodic boundary condition for molecular systems?

Reading some Gaussian related documents (inputs, manuals, books), I found the possibility to setup periodic boundary conditions (PBC) in Gaussian. As Gaussian is developed only for molecular systems ...
Camps's user avatar
  • 23.6k
13 votes
2 answers
328 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 ...
vkj's user avatar
  • 191
13 votes
1 answer
2k views

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

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 ...
johnymm's user avatar
  • 231
12 votes
3 answers
598 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) ...
Alex I's user avatar
  • 1,038
12 votes
1 answer
846 views

What is Gaussian16's read-file logic when using ONIOM with genecp?

I want to use the ONIOM keyword, like oniom(ccsd(t)/avtz:m06/genEcp) or similar, in conjunction with genecp. I want to use ...
jtyang's user avatar
  • 295
12 votes
1 answer
536 views

Calculate spin-spin coupling based on previous GIAO calculation with Gaussian

I used GAUSSIAN/GAUSSVIEW to calculate the GIAO Magnetic shielding tensor (ppm), but I forgot to calculate the Nuclear spin-spin coupling J (Hz). How can I use the .chk file or .log file to calculate ...
lay lay's user avatar
  • 121
11 votes
2 answers
1k 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: ...
aerospace's user avatar
  • 193
11 votes
3 answers
733 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 ...
Paul Logan's user avatar
11 votes
1 answer
1k 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 ...
user avatar
11 votes
1 answer
397 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 ...
Tristan Maxson's user avatar
11 votes
1 answer
251 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 ...
Greg's user avatar
  • 1,807
10 votes
4 answers
2k 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 ...
neco's user avatar
  • 1,789
10 votes
4 answers
2k 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 ...
mykd's user avatar
  • 2,342
10 votes
2 answers
1k 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 ...
astha's user avatar
  • 1,673
10 votes
1 answer
583 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. ...
J.Doe's user avatar
  • 493
10 votes
2 answers
2k 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 ...
christian's user avatar
  • 103
10 votes
1 answer
1k 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 ...
sarra6's user avatar
  • 579
10 votes
1 answer
200 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 ...
Roman's user avatar
  • 2,373
9 votes
3 answers
1k 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, ...
S R Maiti's user avatar
  • 7,011
9 votes
3 answers
421 views

The number of orbitals in Gaussian/GAMESS log file

After calculating the energy of a $\ce{CH4}$ molecule with a 6-31G(d,p) basis set, I obtained the Gaussian/GAMESS log file and describe a part of the log file as follows. ...
neco's user avatar
  • 1,789
9 votes
1 answer
376 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 ...
astha's user avatar
  • 1,673
9 votes
1 answer
821 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 ...
Protima Rani Paul's user avatar
9 votes
1 answer
317 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: ...
Bruno's user avatar
  • 233
9 votes
1 answer
102 views

Too large value of s-orbital in near nucleus

After my previous question (here), I'm now studying the orbitals actually used in Gaussian through calculating them myself using Basis Set Exchange data. However, I found that some orbital exponents ...
neco's user avatar
  • 1,789
9 votes
1 answer
624 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-...
Roman's user avatar
  • 2,373
9 votes
0 answers
115 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 ...
evd's user avatar
  • 91
8 votes
2 answers
2k 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 $2p_x$, ...
neco's user avatar
  • 1,789
8 votes
2 answers
297 views

Geometrical Optimization not converging for a double perovskite quantum dot, using Gaussian

I am trying to optimize the geometry of a Cs4CuSb2Cl12 Stoichiometric Quantum dot and I have checked the input multiple times, but the opt+freq calculation is not converging. The quantum dot has about ...
Parmeet Singh EP 066's user avatar
8 votes
1 answer
237 views

Compute polarizability after each step of relaxed scan in Gaussian 16

I am computing a relaxed 2D scan with Gaussian 16 in order to reproduce some computational data. I am interested in computing the dipole moment vector and the (static) polarizability matrix after each ...
capitn96's user avatar
8 votes
2 answers
3k 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 ...
sarah bnm's user avatar
8 votes
2 answers
675 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 : ...
Atom's user avatar
  • 1,005
8 votes
1 answer
219 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 ...
sarra6's user avatar
  • 579
8 votes
1 answer
261 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 (...
Yassamine's user avatar
8 votes
1 answer
746 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 ...
Andrea Pellegrini's user avatar
8 votes
1 answer
71 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 ...
Andrea's user avatar
  • 856
8 votes
1 answer
994 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'...
In_Chem's user avatar
  • 81
8 votes
1 answer
358 views

Is this G16 molecular hyperpolarizability error reproducible in other software?

I was trying to calculate the hyperpolarizability $\beta$ of a cluster of two water molecules in Gaussian16 using the route card: ...
mykd's user avatar
  • 2,342
8 votes
1 answer
216 views

Optimizing (DFT/MP2) small molecule dimers

I'm attempting to optimize n-alkane dimers using MP2/DFT in Gaussian09. However the first one or two frequencies are always negative. Can these modes be ignored or do I need to do a tighter ...
Subrata Tewary's user avatar