All Questions
Tagged with intermolecular-forces quantum-chemistry
20 questions
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How to calculate the ground state molecular potential curve of Lithium in different spin configuration?
I am a physics student and interested in Atom, and molecule optical physics. I am studying Feshbach resonance and I need to know the potential curve of the molecule, then I ask question in physics ...
- 111
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1
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57
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Analog of chemical accuracy in vibronic energy calculation [closed]
Is there any analog of chemical accuracy in vibronic energy calculation? I understand that the unit is /cm however, probably, I shouldn't expect a given number in that unit as the analog.
I am ...
- 245
1
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301
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Physical origin of induction and dispersion energies
I am reading this book on non-covalent interactions. Chapter 1 states that there are 3 types of non-covalent interactions:
Electrostatic interactions, which are just the coulomb interactions between ...
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0
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Charge polarisation in acetamide molecule due to different lithium salts (varying anions)
I am trying to understand how will acetamide molecules behave in the presence of lithium salts with different anions (nitrate, bromide and perchlorate).
Among the three, it is evident that bromide is ...
- 111
6
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296
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Casimir effect and van der Waals forces
The Casimir effect makes two close metal plates in a vacuum attract.
I was pondering and figured out that two close molecules should experience the same effect, as they are close and between molecules ...
- 63
3
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175
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What are the cheapest basis sets able to model intermolecular dipole interactions inside a metal complex and give good relative energies, with DFT?
As a example, If I have a square planar complex of a cation with both a weakly polar ligand (X) and strongly polar ones, like ammonia and water I expect a bit of stabilization due to formation of a ...
- 663
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117
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Is Tkatchenko's MBD-NL method self-consistent?
I have a question regarding Tkatchenko's [1] new nonlocal many-body dispersion method (MBD-NL). Does anyone know if it's a self-consistent method? I read this paper many times but I'm still not sure.
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4
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Hessian Matrix and Physical directions: Potential Energy Surface
How do the eigenvectors of the Hessian Matrix for potential energy surface correspond directly to the physical directions of translation, rotation and vibration?
I see that they might correspond to ...
- 1,171
8
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How to obtain curve energy and non-bonded interaction parameters (e.g. Lennard Jones parameters) with Gaussian?
I am parameterizing a force field and would need to obtain non-bonded interaction parameters of atoms (e.g., Lennard-Jones parameters).
My primary idea is to obtain a potential energy curve using the ...
- 321
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2
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How are London Dispersion Forces generated?
While talking about the gaseous state of matter we came to the topic of London Dispersion Forces caused by the generation of a dipole in one atom which induces a dipole in another. While talking about ...
user84548
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Why does the exchange interaction in Hartree-Fock theory lower the total energy?
In Hartree-Fock theory, the expectation value of the total energy can be written as
$$E = \langle\Psi| H |\Psi\rangle = \sum_{a} \langle a| h |a \rangle + \frac{1}{2}\sum_{ab} \big( [aa |bb] - [ab|ba]...
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Radial pair distribution function (VMD). How to define it for a water NaCl system with multiple Na and Cl?
I'm struggling to understand a paper in which someone has presented radial distribution functions (RDFs) for a system that contains multiple Na, Cl, and water atoms/molecules. I don't know exactly ...
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292
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Van der Waals interaction and magnetic dipole dipole interaction
I have a conceptual question that bothers me.
From what I understand, van der Waals forces are the primary source of inter-molecular interaction. There are three different possible origins for van ...
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7
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How to calculate Lennard-Jones potential with quantum mechanical methods
I want to know the procedure to calculate the Lennard-Jones potential for a metal-halogen pair (specifically vanadium-chlorine). Is it possible to calculate using any QM packages like Mopac, NWChem, ...
- 517
4
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Do dipole dipole interactions need to be added explicitly to vdW forces while doing DFT simulations for organic molecules?
I am modelling the adsorption of organic molecules on metal surfaces using plane-wave dft. While there is literature on how important van der Waals forces are for organic systems, and there are also ...
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2
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1
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Recommendations for electrostatic potential surfaces
Are there standards for density cutoffs, colours and colour mappings for electrostatic potential surfaces?
I observe that people use many different values.
For instance, this article (in Fig. 1a) ...
- 2,883
34
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8k
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What is the exchange interaction?
As the wikipedia article for the exchange interaction so aptly notes, exchange "has no classical analogue."
How wonderful.
Exchange shows up essentially while enforcing the condition that two ...
- 13.2k
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Fitting of interatomic potentials to a training set
I have read several times in the literature the following:
"The fittings were accomplished using a combination of the singular value decomposition method for linear parameters and the Simplex method ...
- 79
24
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3
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Is Hydrogen Bonding a Type of Dipole Dipole Interaction?
I understand that dipole dipole forces is due to the attraction of the different partials charges of atoms in different molecules due to their different electro-negativities.
For hydrogen bonding, ...
- 7,462
4
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1
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Charge consistency in fragment qm/mm methods
I'm calculating the multipole moments on several fragments of a molecule. What are some procedures to ensure that the charges etc are representative of the complete molecule? How do I ensure I'm not ...
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