Questions tagged [geometry]

Questions about molecular or lattice geometry.

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8 votes
1 answer
157 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 ...
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7 votes
2 answers
331 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?
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  • 527
9 votes
1 answer
148 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 ...
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  • 527
11 votes
1 answer
180 views

How would one find a material's equilibrium structure at any specific temperature?

Let's take an example of a simple FCC material, a binary alloy. Above absolute zero K, the alloy will start to disorder and become an FCC solid solution. The alloy would develop defects as it ...
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7 votes
2 answers
494 views

Converting input file into XYZ format using ASE

Here is my code: ...
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  • 715
2 votes
1 answer
46 views

Determining the geometry of UOx and WOx for (x=1-3)

Is there a way to work out the geometries for the $\ce{UO_x}$ and $\ce{WO_x}$ species for ($x=1-3$). I know that deducing the multiplicity (the number of unpaired electrons) in d and f block ...
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  • 821
11 votes
1 answer
126 views

Translating fractional coordinates resulting from conventional cell and primitive cell

I have calculated the band structure of some material where the unit cell was the conventional one (i.e. the lattice vectors are orthogonal). I'm trying now to calculate the same band structure only ...
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  • 111
8 votes
0 answers
105 views

References related to the molecular distance geometry problem (estimating true distances based on noisy distances)

One aspect of the molecular distance geometry problem (MDGP) described in this PDF, can be written as follows: "Given observations of noisy distances between atoms in a molecule, estimate the ...
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  • 189
13 votes
1 answer
201 views

Extracting molecular structure from CIF file using VESTA or Mercury

I am trying to extract XYZ coordinates from a CIF file for a molecule to use in DFT calculations. I have Mercury and Vesta installed on my computer. Whenever I open the files, I get the following ...
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9 votes
1 answer
184 views

How do I create geometry files for carbon nanoribbons and molecular junctions for DFTB+?

I am currently learning DFTB+ using the tutorials on the official website : Carbon Nanoribbons : https://dftbplus-recipes.readthedocs.io/en/latest/defect/carbon2d-elec.html#zigzag-nanoribbon ...
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16 votes
6 answers
3k views

How to make a python code that can read a .xyz file and find the distance between atoms?

I want to make a python script that will load an xyz file. From the xyz parameters, I need to find the distance between atoms, angle and dihedral between atoms. The file xyz have this structure: ...
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12 votes
1 answer
173 views

Functional group detection from geometry

I am currently looking for an efficient way to detect common functional groups - that is, characterize whether a molecule is an alcohol, an aromatic compound, etc. - in a larger database consisting of ...
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11 votes
1 answer
169 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 ...
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  • 1,638
9 votes
1 answer
269 views

What is the "formula unit surface area"?

Firstly, sorry if this question is too basic for this community but seriously I couldn't find any answer. Does it mean the multiplication of the in-plane lattice constants? For example, lets say ...
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  • 1,011
11 votes
3 answers
155 views

Rotation of crystal structure to match another structure of the same compound/polymorph

Say, I have two crystal structures of a particular organic molecule, the crystal structures are basically identical, apart from a rotation and redefinition of the lattice vectors/angles, a simple ...
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5 votes
1 answer
259 views

Is there a difference in performance when the symmetry is specified via ibrav in Quantum ESPRESSO?

I have been using cif2cell for converting CIF files into quantum ESPRESSO input files. But cif2cell always keeps the ibrav value to be zero and indicates the CELL_PARAMETERS. As per the quantum ...
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  • 4,268
19 votes
4 answers
1k views

How to explain Miller indices to someone outside nanomaterials?

I often find that when talking to experimentalists outside of the field of nanomaterials, it is nearly impossible to explain Miller indices concisely. As this often comes up during talks from other ...
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10 votes
0 answers
285 views

Constraining coordination or bond lengths for certain atoms in VASP [closed]

I have a structure composed of many MX4 tetrahedral units. When doing MD on this structure I find that just one M atom moves into a trigonal planar coordination (MX3). I was wondering how to set ...
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  • 1,040
5 votes
1 answer
353 views

How to calculate RMSD with GLIDE?

I need to calculate the RMSD between a co-crystallized ligand and my ligands and a non-co-crystallized ligand with GLIDE but I don't know how. Could someone explain to me how to do it? Many thanks in ...
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  • 457
14 votes
3 answers
1k views

Geometry optimization for n-layers in VASP

What is the best way to optimize monolayer geometry in VASP? Should the same method be used for an n-layer (n=2,3,4,5)?
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18 votes
2 answers
949 views

Logic of published geometry optimization results without checking phonons

I see that in many papers where optimization results presented, they do not mention phonons and their force convergence criterion is 0.01 eV/A. Can you publish a result like that? And is not this ...
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  • 781
4 votes
1 answer
87 views

How much energy difference could be used to distinguish optimized results from different initial geometries for the same structure?

Is there a threshold? Could I say that my final geometries are the same with 'energy difference = 0.05 meV/atom' ?
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  • 1,859
10 votes
2 answers
259 views

What are the methods that can be used to ensure that an optimized geometry is a local minimum?

Usually it is suggested to do a phonon calculation. What are the other ways?
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