Questions tagged [spectroscopy]

For questions about or related to spectroscopy.

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27 votes
2 answers
2k views

Is it right to neglect very small imaginary frequencies?

I'm running a DFT optimization (B3LYP/def2-TZVP) and frequencies in ORCA for a molecule. And I get one or two very small (1-6 cm^-1) imaginary frequencies which corresponds to a slight bend of the ...
Roman's user avatar
  • 2,373
13 votes
1 answer
921 views

GUI for DFT calculations

I am a beginner in DFT. Can someone suggest a good DFT software with a GUI for simulating dipole moments and optical absorption spectra in an organic crystal? I have tried the Burai GUI of Quantum ...
Aswin Alex's user avatar
17 votes
5 answers
3k views

Bond length from infrared spectra?

It's been taught by my lecturer that infrared (IR) spectra are widely used for chemical bonding determination. My question is: is it possible to calculate bond lengths according to the IR spectra? If ...
Rizky Arief S's user avatar
23 votes
1 answer
2k views

How exactly does one compute the vibrational density of states from the output of a molecular dynamics simulation?

There are many things that can be done with the output of a molecular dynamics simulation, but one of the more powerful things is the ability to compute the vibrational density of states (or the ...
jheindel's user avatar
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15 votes
5 answers
2k views

What's the point of doing high accuracy spectroscopy calculations?

I am currently reading Dickenson et al. (2013) The Fundamental Vibration of Molecular Hydrogen. I am trying to understand why this calculation is important for the field beyond basic scientific ...
Omar Shehab's user avatar
13 votes
2 answers
641 views

How to export a calculated Raman spectrum in Q-Chem, as a Gaussian profile?

Does anyone know how to export a calculated Raman spectrum (my calculation was performed in Q-Chem) as a data-file, which can be used to plot the profile of a Gaussian-shape spectrum (in origin, excel,...
Dmitry Eremin's user avatar
12 votes
2 answers
689 views

Recommended code to do XAS/XES/RIXS calculations with?

I am a grad student looking to simulate several XAS/XES and potentially RIXS spectra for some strongly correlated metal-oxides. The materials in question will likely require solving the Bethe-Salpeter ...
Haru Fujimura's user avatar
9 votes
1 answer
327 views

Phonon Calculations and Vibrational Modes

The Raman spectrum of a material shows certain 'active' modes for which we get experimental signatures. Phonon calculations are mostly used to calculate vibrational modes. How can we determine the ...
Shahid Sattar's user avatar
9 votes
1 answer
118 views

Package for computing properties of excited vibrational states

We're starting to develop some calculations of the hyperfine parameters (electric field gradient, spin-rotation coupling, spin-spin coupling) with CFOUR, and we reached a limitation of the public ...
Patrick's user avatar
  • 99
7 votes
0 answers
51 views

How are nematic phases modelled? [closed]

Nematic phases in superconducting materials are studied in both angular-resolved photoelectron spectroscopy (ARPES) and second harmonic generation (SHG) experiments. What techniques, if any, are used ...
2ndQuantized's user avatar
  • 1,021
1 vote
1 answer
26 views

Algorithm for finding the v=1 state of an H2O molecule

In the context of simulating the dissociation dynamics of an H₂O molecule on a metal surface, what algorithm is employed for generating the initial state of a tri-atomic non-linear molecule, such as H₂...
Nidhi Tiwari's user avatar