Questions tagged [intermolecular-forces]
The forces, either attractive or repulsive, that exist between molecules due to electric charges or varying electron cloud distribution. This tag could also include intra-molecular attractions (within one molecule itself) often found in a protein amino acid residues.
69 questions with no upvoted or accepted answers
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Which potentials are suitable for molecular dynamics simulation of simple explicit solvents?
Which potentials (force fields) are suitable for adequately simulating (mixtures of) explicit solvents? Interesting rheological properties include viscosity, surface tension, heat capacity.
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Does water really have strong EM absorption at 3 kHz in solid and 2 GHz in liquid? Why the huge shift?
While writing this answer to the question Transmitter receiver coil separation for Electromagnetic Terrain Conductivity Measurement I ran across this large PDF file of a book Soil and Environmental ...
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Why do chlorinated silanes have lower boiling points than their methane analogs?
The boiling points of the chlorinated silanes and methanes are given below:
$$\begin{array}{ccc}
\hline
\text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
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Why does diethylmethylamine have such a low melting point?
According to PubChem, diethylmethylamine has a remarkably low melting point of $-196.0\ \mathrm{^\circ C}$. This is substantially lower than the melting points of dimethylethylamine ($-140.0\ \mathrm{^...
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Are all humectants sticky?
While using a topical lotion based on ethanol, water and propylene glycol, I noticed that it becomes sticky while drying. Propylene glycol is a humectant and is used for this purpose in ...
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How can copper(II) sulfate crystallize outside a glass vial?
I'm making copper sulfate crystals in glasses. Within a few weeks, the copper sulfate seems to crystallize both inside and outside the glass:
(A few weeks after making a new solution)
(Yet another ...
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Intermolecular Forces in Teflon vs Polyethylene
From Wikipedia, polyethylene has a melting point of around $400K$, while Teflon (polytetrafluoroethylene) has a melting point of $600 K$, which is much higher. Besides the increased London Dispersion ...
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What explains the relative order of melting and boiling of oxygen and nitrogen?
Why is the melting point of nitrogen ($\ce{N2}$) greater than that of oxygen ($\ce{O2}$)? After all, both are non-polar, and $\ce{O2}$ has more electrons than $\ce{N2}$.
In addition, why is the ...
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Is there experimental evidence to show boiling point increases with external electric field, and if so, by how much?
I was wondering whether anyone has demonstrated that a liquid will have a higher boiling point if it is placed in a very large electric field. I believe to be the case, since induced dipoles would be ...
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Calculating volume ethanol in an fermented aqueous solution of sucrose, water, and ethanol
I've been working on a biology experiment where I calculate the fermentation yield of yeast under various light induced stress responses inhibiting the translation of various fermentation enzymes. My ...
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Is it possible to have an anhydrous solvent for virology, specifically in vitro phage assembly?
Typical protocols for lambda phage in vitro assembly call for you to dump all your viral components and buffer solutions into water. Water is a great solvent, drives extraction of energy from atp, and ...
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Why do fluoride molecules seem to have abnormally low boiling points?
As far as I know, to non-polar molecules like CF4 and C2H6,
boiling point is mainly affected by the London dispersion force.
As a result, molecules with more protons and electrons normally have higher ...
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Why ethyl cyanide and propanol have the same boiling point?
As I understand, the intermolecular forces of ethyl cyanide are of van der Waals nature (dipole-dipole) but in the propanol molecule there are hydrogen bonds which are in principle much stronger. Why ...
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Why is boiling point of carbon tetrachloride greater than silicon tetrachloride?
$\ce{CCl4}$ and $\ce{SiCl4}$ both are non polar molecules thus London forces must be the only forces of interaction.
Then London forces are supposed to be greater in $\ce{SiCl4}$ due to its larger ...
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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 ...
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Why is this scintillator component turning into a milky-white emulsion?
I am a chemistry and physics double major doing some chemistry work in a nuclear physics lab. My mentor is a physicist, so his area of expertise is occasionally mismatched with what I need for my ...
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How to illustrate London forces?
This may be too subjective for this forum, but I'll take my chances.
For the purposes of a "quick and dirty" illustration of London forces, I'm looking for best practices and creative ideas. For ...
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Can Ion-Dipole Force Occur Between Lecithin and Water?
So, ion-dipole force occurs between an ion and a polar molecule. I would like to ask if an ion-dipole force would occur between water molecules and lecithin as seen in the picture, since it has a ...
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How to model a molecule of benzene surrounded by 100 molecules of water with molecular dynamics?
I have experience calculating molecular properties (mostly DFT). However, I would like to spend some time on molecular dynamics methods. I would like to ask your advice to direct me towards a program ...
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Boiling points of ethylene, formaldehyde and oxygen
The boiling points of ethylene, formaldehyde and dioxygen are $\pu{-103.7 ^\circ C}$, $\pu{-19 ^\circ C}$, and $\pu{−183 ^\circ C}$, respectively. I expect formaldehyde to have the highest boiling ...
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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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Why don’t compounds with high boiling points not necessarily have high attraction constants (a) in the Van der Waals equation?
You can find a list of constants $a$ and $b$ for the van der Waals equation in a Wikipedia website. Accordingly, hexane has a higher attraction constant ($a$) than that for water (24.71 vs 5.536), but ...
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Why do stronger intermolecular forces lead to a larger change in temperature?
We performed an experiment where tissue paper soaked in various chemicals was wrapped around the end of a temperature probe.
The chemicals with stronger intermolecular forces had a smaller drop in ...
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Calculate activation energy of intermolecular displacement on a nano particle
I'm simulating a nano particle and wish to calculate the activation energy of the reaction where an atom is displaced from one point on the lattice to a neighboring void( might be at higher energy ...
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Work to overcome adhesion of a liquid to a solid
I'm interested in the van Der Waals force of a liquid adhered to a solid. For example, if you spray some water on a vertical piece of glass, the little droplets with adhere to the window rather than ...
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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 ...
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Solvation rates of crystalline and noncrystalline materials
Assuming equal surface area (and other variables), would a highly ordered crystal of some substance dissolve more slowly or quickly than (or at the same rate as) a disordered sample of the same ...
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Boiling point and Intermolecular forces
After looking for proper reasons for boiling point orders, nobody could even explain why $\ce{CCl4}$ has a higher boiling point than $\ce{SiCl4}$, but after looking for patterns, in lots and cases of $...
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Structure of fluoroalkylsilane
I want to use FAS (fluoroalkylsilane) in my molecular dynamics study. How can I find it's real structure? So that I can find proper forcefield for simulating the molecule. It would be very nice if you ...
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why Tin/Zinc alloys can be used to solder aluminum and Tin alone does not "wet" the aluminum?
It is impossible to solder aluminum with only tin, tin does not "wet" aluminum surface because of the instantaneous reaction aluminum/oxygen on the surface of the base metal (aluminum). I ...
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Why does Ethylene Glycol have higher boiling point than Propylene Glycol?
Looking at the two alcohols, both have hydrogen bonding and are singly bonded throughout the molecule. However, propylene glycol has a larger electron cloud which to my knowledge would increase its ...
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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 ...
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Air/Acetonitrile Interfaces
Say I drop some acetonitrile on a grounded surface and it forms a meniscus. The acetonitrile is in air. Lets forget about evaporation for the moment.
Will there be an interfacial dipole formed by the ...
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Interaction energy of an hydroxide ion with a Pd surface
I need to estimate the interaction energy of a hydroxide ion with a palladium surface of $-0.6$V in water.
I know that the electric field of a charge $e$ is
$$
E = \frac{1}{4\pi\epsilon}\frac{e}{r^2}
$...
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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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Intermolecular Forces and State Change
I know that intermolecular forces determine the state of a substance at a given temperature and that changing state involves the ability of a substance to overcome those forces. I encountered a ...
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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 ...
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Do CHF3 and acetone form a hydrogen bond?
I haven't been able to find a reference confirming that fluoroform forms hydrogen bonds with acetone. Do they?
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Pressure of a system of particles
I'll derive the pressure of a system of particles, which would be used in a MD simulation for example, according to Allen's Computer Simulation of Liquids and show where my issue is.
Consider a ...
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Why are Buckminsterfullerene (C60) solutions pink/purple?
A solution of Buckminsterfullerene $\ce{(C60)}$ is shown below:
According to the April 8th Wikipedia page on Buckminsterfullerene $\ce{(C60)}$:
Solutions of pure C60 have a deep purple color which ...
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Solubility of alcohols in non-polar solvents
The solubility of an alcohol in a non-polar solvent (like hexane) increases with size of the alcohol, as the non-polar chain increases. However, as the chain keeps increasing, will the solubility ...
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Why does chlorine gas have a higher boiling point than hydrogen iodide
Hydrogen iodide, $\ce{HI}$, is a dipolar molecule much larger than chlorine, $\ce{Cl2}$.
The melting point of $\ce{HI}$ $(222.35\ \mathrm K)$ is definitely higher than that of $\ce{Cl2}$ $(171.6\ \...
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Condensation point of molecule compounds?
Which of the following gasses will condense at the lowest pressure (Assuming temperature is held constant)?
$\ce{CBr4}$
$\ce{CH2Br2}$
I believe that compound 2 will condense at the lower pressure ...
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Is the 12-6 Lennard Jones potential a good description of van der Waals interaction energy?
It seems to me that the Lennard Jones potential oversimplifies the more complex nature of van der Waals forces. However, in most of the MD simulation package, this is generally accepted.
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Non-covalent interactions
According to Keesom, Debye and London effect, the non-covalent reactions should be stronger, the bigger are electric charge differences between two interacting particles. E.g. Ion-induced dipole are ...
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Why do intramolecular forces weaken due to heat?
In my most recent research into thermoplastics, I was unable to find any information regarding what actually happens to intramolecular forces when heat is applied.
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What radius best represents reaction distance?
Molecules must be within a certain distance for a reaction to begin as well as satisfying a myriad of other factors. Whilst the exact distance varies from reaction to reaction, is their any distance/...
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How do you know what inter-molecular interactions are present?
I'm studying for a chem exam and there are often questions of this form: What kind of inter-molecular interactions are important in (insert compound here). Then the possible answers are any ...
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Is the momentary dipole in between a cell membrane due to the van-der-Waals forces?
There are van-der-Waals forces within non-polar molecules. I read it that is mainly due to the instantaneous movements of the electron cloud's distribution. When looking at symmetrical molecules like $...
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Incompatibility of Helmholtz Double Layer and Redox electrochemistry
In an electric double layer capacitor(EDLC) (or any situation with a Helmholtz double layer) what prevents the ions from being reduced or oxidized like the ions in an electrochemical cell?
If it is ...
