Scientists explore the origins of energy in chemical reactions using experimental quantum chemistry

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Scientists explore the origins of energy in chemical reactions using experimental quantum chemistry

Post by Cr6 on Sun Aug 23, 2015 1:37 am

Scientists explore the origins of energy in chemical reactions using experimental quantum chemistry
August 21, 2015 by Lisa Zyg
(more at link)

Read more at: http://phys.org/news/2015-08-scientists-explore-energy-chemical-reactions.html#jCp

http://phys.org/news/2015-08-scientists-explore-energy-chemical-reactions.html

Summary

(Phys.org)—One thing that all chemical reactions have in common—whether they are the reactions that take place inside a battery, the metabolic reactions inside a living organism, or the combustion reactions that cause an explosion—is that they all involve some kind of change in energy. On a large scale, the changes in energy of a reaction can usually be measured in various ways for practical purposes, but attempting to understand the fundamental origins of this energy at smaller and smaller scales becomes more complicated, especially as chemistry enters the quantum realm.

In a new study, Cornell University chemists Dr. Martin Rahm and Prof. Roald Hoffmann (who received the Nobel Prize in Chemistry in 1981 for theories on the course of chemical reactions) have explored a new way of understanding the origins of energy in chemical reactions at the quantum level. Their paper is published in the Journal of the American Chemical Society.

Energy breakdown

At the heart of the paper is the idea—which is generally widely accepted in chemistry—that all of the interactions between the molecules, atoms, and the electrons that bind atoms together can collectively be understood in terms of energy. However, the origins of this energy, and how the energy changes during a chemical reaction, remains an open question. Over the years, researchers have proposed various "energy decomposition analyses," or interpretations of how this energy can be broken down.

In their paper, Rahm and Hoffmann propose a new energy decomposition analysis in which the total changing energy of any chemical reaction can be broken down into three components: nuclear-nuclear repulsion (the repulsive energy between the positively charged nuclei of different atoms), the average electron binding energy (the average energy required to remove one electron from an atom), and electron-electron interactions (the repulsive energy between negatively charged electrons).

To paint a picture of how this works, the scientists explain in their paper what happens when any two atoms are brought closer together. First, the repulsion between the two nuclei increases, which causes the electrons to move in between the nuclei in an attempt to shield some of this repulsion. In the presence of the two nuclei, the average binding energy of the electrons changes due to differences in electron-nuclear attraction. As the electrons move closer together, they also begin to interact more strongly with each other. Quantifying these electron-electron interactions is one of the greatest challenges in computational chemistry.

One thing that this work demonstrates is that it is possible to estimate these electron-electron interactions (the third term) from experimental data. As the scientists explain, this is one area where chemistry becomes "quantum," and has not been measurable before now.

"Traditionally, knowledge of electron-electron interaction energies has only been attainable by first mathematically constructing a wave function and then approximating a solution to the so-called Schrödinger equation, i.e., by doing quantum mechanics," Rahm told Phys.org. "This work demonstrates that such information can actually be extracted from sufficiently accurate experimental data. There are caveats and inherent approximations, but it is in principle possible."

Measuring electronegativity

Other new possibilities arise from understanding the second term—the average electron binding energy—as an alternative interpretation of one of the most fundamental concepts of chemistry, that of electronegativity. As the scientists explain, electronegativity was traditionally defined by Linus Pauling in 1932 as "the power of an atom to attract electrons to itself," and in this way it tells where electrons move when two or more atoms come together, which is the basis of bond formation. This is still the most widely used definition today.

An alternative definition, proposed in 1989 by Lee Allen, is that electronegativity is the average binding energy of valence electrons (however, Rahm and Hoffmann use all of the electrons, not just the valence ones, in their energy partitioning proposal). Electronegativity values obtained using Allen's definition correlate strongly with those obtained using Pauling's, but the main advantage of Allen's definition is that electronegativity defined in this way can be experimentally measured (such as by using photoelectron spectroscopy), while electronegativity using the Pauling definition cannot be.



From fundamental understanding to practical use


The ability to experimentally measure the average electron binding energy, along with the fact that experimental data can be used to determine nuclear-nuclear repulsion and electron-electron interactions, provides some unprecedented abilities. Most importantly, it makes it possible to experimentally measure what percentage of the total energy change that each of the three components is responsible for.

With this information, the scientists explain that all chemical reactions and physical transformations can be classified into eight types based on whether the reaction is energy-consuming or energy-releasing, and on whether it is favored or resisted by the nuclear, multielectron, and/or binding energy components. This information can provide valuable information about the nature of a chemical bond. The researchers also showed that, in four of the eight classes of reactions, knowledge of the binding energy alone (and by extension, either definition of electronegativity) is enough to predict whether or not the reaction is likely to proceed. In other words, as the scientists explain, "it allows researchers to predict when simple and intuitive rationales using the time-honored concept of electronegativity will work in predicting trends in energy, and when it will fail."

This paper is the first in a series in which the researchers plan to explore these ideas further, especially in regard to the potential usefulness of this new perspective of energy in chemical reactions. They note that one "tantalizing" prospect is the possibility to measure absolute energies, whereas most of chemistry relates to the measure of relative energies. An experiment would begin with the known measured absolute energy of a one-electron system (such as C5+, which is a carbon atom with all but one of its electrons removed), which can easily be measured since, with only one electron, there is zero electron-electron repulsion. Then the absolute energy of the carbon atom, and the electron-electron interactions within it, could be measured as electrons are added back one by one. This feat should be possible since it's in principle possible to experimentally measure the average electron binding energy for each step. In this way, an alternative understanding of the fundamentals of chemistry may provide useful new tools and applications.

"This paper has three important outcomes," Rahm said. "It connects the central chemical concept of electronegativity with the total energy, whose changes govern most of chemistry. It tells us how we can estimate the importance of electron-electron interactions in governing chemical reactions, from experimental data. It is also the first energy decomposition scheme that can be interchangeably applied using either or both computed and experimental data. This should allow for quite some interdisciplinary bridging."


Read more at: http://phys.org/news/2015-08-scientists-explore-energy-chemical-reactions.html#jCp

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Re: Scientists explore the origins of energy in chemical reactions using experimental quantum chemistry

Post by LongtimeAirman on Wed Aug 26, 2015 8:57 pm

Cr6, Thanks for the posting. I think this is a Miles worthy study.

Before I even read it I was put-off by the thought of Quantum Chemistry.  I was also confused by the graphene molecular diagram included - after you had announced your Graphene interest and shotgun three or so new threads (see, my imagination still gets me into trouble). On the Atomic Viewer thread (http://milesmathis.the-talk.net/t114p15-atomic-model-editor#861), I had just asked;
LongtimeAirman wrote:Do molecular bonds take or create energy in their formations?
Nevyn gave what I think is a definitive answer:
"I would say that molecules change the ambient field in their local area, as compared to that field with the individual atoms in it. This can be measured as an increase or decrease in energy because such measurements are made with respect to the ambient field. I think a molecule must use the charge field in a more efficient manner than its components could, otherwise, why would it form? So in most cases, a molecule will channel more charge than the sum of its atoms and it will do it more effectively. It is hard to say exactly what 'effectively' means as it changes in different circumstances. It may make the molecule radiate more charge making it stronger, that is, it can repel attacks from other particles more easily. It may make the molecule more magnetic if the charge is channeled out the equator. It may make it more electric if it handles through-charge better. It may appear to take heat from the area if it changes the ambient charge into something else (photons, electric current, etc) or it may add heat which the first example of a radiating molecule would do.”
Later in the thread, Nevyn added
“any charged particle defies entropy because it creates order from disorder. Although, I don't believe in entropy as order, myself.”
All that fits easily into my understanding.

From the subj article (above);
“At the heart of the paper is the idea—which is generally widely accepted in chemistry—that all of the interactions between the molecules, atoms, and the electrons that bind atoms together can collectively be understood in terms of energy. However, the origins of this energy, and how the energy changes during a chemical reaction, remains an open question. Over the years, researchers have proposed various "energy decomposition analyses," or interpretations of how this energy can be broken down”
The team endeavored to measure three force interactions: 1) Nuclei repulsion; 2) Binding energy; and 3) Electron repulsion. The only supposed attraction interaction – Binding energy – we understand to be charge channel flow rate changes that occur when main axis electrons are presence or absent, and the fact that those electrons must be removed from their positions in order to achieve proper molecular bonding. I assume binding energy is closely related to the Ionization energy. It’s certainly not attraction.

QM is just “cover” for a team which is trying to obtain new, very low level, nucleus - nucleus or electron-electron, repulsion energy experimental data. It seems that energy in versus energy out has become somewhat ambiguous given the eight types of reactions they have categorized.

Of course I haven’t seen that data, but IMO this teams’ results should provide plenty of unintended support for Miles’ nuclear ideas. For example, I would expect such anomalous findings as – “nucleic repulsion as a function of angle” - grist. I imagine (?) these energy levels can be used to “calibrate” the Atomic Viewer.

The physics world is turning from the weight of ongoing experimental results that cannot be explained by QM. For us, things are slowly falling into place.

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Re: Scientists explore the origins of energy in chemical reactions using experimental quantum chemistry

Post by Cr6 on Thu Aug 27, 2015 2:06 am

The team endeavored to measure three force interactions: 1) Nuclei repulsion; 2) Binding energy; and 3) Electron repulsion. The only supposed attraction interaction – Binding energy – we understand to be charge channel flow rate changes that occur when main axis electrons are presence or absent, and the fact that those electrons must be removed from their positions in order to achieve proper molecular bonding. I assume binding energy is closely related to the Ionization energy. It’s certainly not attraction.

QM is just “cover” for a team which is trying to obtain new, very low level, nucleus - nucleus or electron-electron, repulsion energy experimental data. It seems that energy in versus energy out has become somewhat ambiguous given the eight types of reactions they have categorized.

Of course I haven’t seen that data, but IMO this teams’ results should provide plenty of unintended support for Miles’ nuclear ideas. For example, I would expect such anomalous findings as – “nucleic repulsion as a function of angle” - grist. I imagine (?) these energy levels can be used to “calibrate” the Atomic Viewer.

Yeah, that's why I'm keeping an eye on these types of sites. They apparently are just publishing this without worrying about QM as much as they might have a few years ago.

This paper from Mathis is pretty good on ionization. I'm surprised that as much as "Plasma" gets attention from the TB people, that they don't question the energy transfers with more critical insights -- scaled from the element up to Galaxies.  It is just taken as a physical "given" with current physics. I haven't seen much QM publications on Plasmas that made much physical "sense" if you know what I mean.

Your comments made me look up this Mathis paper  geek -- I can't tell if he has "firmed up" the location of his electron "eddies":
-----
 241b. Deuterium and Tritium

That is the He sandwich I was talking about, but here I have drawn all the main charge vectors. From them, you can see that the neutrons must bond in He4 side-to-side. The left neutron is then channeling the anticharge of the upper 2H, but since the bottom 2H is upside-down to the top one, it doesn't feel that charge as anticharge. It is looking at the anticharge from the other direction, so it sees it as charge. Which of course means our two neutrons are reversed. One is upside-down to the other. In some way, it is now an antineutron.

Interestingly, the mainstream knows this, in a way. In this situation, it also admits the neutrons are anti­parallel. However, since according to mainstream theory all spins are intrinsic (not real), the standard model can't use mechanics or diagrams to explain any of this. Of course they do that on purpose. Because they weren't able to explain any of this sensibly and directly decades ago, they just gave up and started calling everything intrinsic or virtual. That way they don't have to draw anything for you or make sense. They can forbid you from trying to visualize it and make sense of it, which is the perfect protection for their half-baked and non-physical theories. It also allows them to fudge equations much more easily, since if you aren't applying the equations to sensible diagrams or firm variable assignments, you don't spot the fudges. The mainstream figured out long ago—following Bohr and Heisenberg and Born—that if you want to sell and protect a theory full of obvious holes, the best thing to do is cloak it as much as possible. And the best way to do that is to bury it under virtual particles and fields and unassigned math, and forbid anyone from trying to visualize it. This is why they start every course on quantum mechanics—first hour, first day—with the warning that none of it makes sense. They tell you there is something wrong with you if you ask it to make sense. They tell you new physics is utterly new and improved, and it is improved because it “transcends” all the old rules about making sense. Physics as modern art, in other words. Selling magic as physics.

In my first attempts to diagram the alpha a couple of years ago, I put the electrons inside the sandwich;  but now you will notice they are outside. It became clear to me that ionization required the electrons to be in the outer eddies, not the inner ones. The Balmer equation also strongly indicated that, with its + and – terms. The way elements ionize before bonding also indicated that, so that is the way I now draw it. However, it may be that the electrons of interior alphas in the architecture of larger elements are driven to the interior positions, and I leave the question open as to whether electrons can inhabit a variety of eddies in the nucleus, depending on the physical situation.

But let us return to 2H, by itself. Why would it be more fragile than 1H? We are told that stars don't commonly produce 2H, or if they do, “they break it up as fast as it is produced.” Why would they do that? Well, we have already seen the answer above: stars are making Helium (3 or 4), and so they don't leave any 2H lying around unbound. This means that they don't break up 2H and that 2H is not really more fragile. Stars don't break it up, they fuse it. Fusing is what I diagrammed above. The heavy charge streams in stars simply make it very easy for those 2H's to come together, and so once the star has produced the Deuterium, the Helium naturally follows.

That begs the question: If that is so, it would mean that stars “naturally” produce exactly equal numbers of up 2H and down 2H, not only globally but locally. If they didn't, some free 2H would certainly be found. How and why do stars do that?

http://milesmathis.com/deut.pdf
and
http://milesmathis.com/diatom.pdf (spin isomers included)

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