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Home / Science / Tech: & # 39; fudge factors & # 39; in physics? Team says it's time to restart – (report)

Tech: & # 39; fudge factors & # 39; in physics? Team says it's time to restart – (report)



Science is ready to make a "quantum leap" as more puzzles arise on how atoms behave and interact with each other.

The field of quantum physics with its complex mathematical equations for the prediction of the interactions and energy levels of Englisch: bio-pro.de/en/region/stern/magazine/…1/index.html Technologies made possible, from computers and Smartphones over lasers up to magnetic resonance tomographs. And experts say that revolutionary progress will come.

But to make a big jump, you have to be physically fit, and researchers at the University of Delaware have found a field of quantum physics that could use even more calisthenics. The research, conducted by graduate student Muhammed Shahbaz with his adviser, Prof. Krzysztof Szalewicz in the UD Department of Physics and Astronomy, was recently published in Physical Review Letters the journal of the American Physical Society [1

9659003] Exactly how People can be attracted to each other atoms, or, well, be repelled. Take Argon – the third most abundant gas in the Earth's atmosphere. This non-reactive gas has a variety of uses, from protecting historical documents to preventing the tungsten filament from being corroded into fluorescent lamps. When two argon atoms are far apart, they are attracted to each other until they reach about 3.5 angstroms and then repel. It's like getting ready to move on after they've looked really good.

But physicists did not discover that two decades ago, when they tested density functional theory (DFT) today is widely used to model and predict the electronic structure of atoms. Most versions of DFT either predicted little or no attraction. Where is the mistake? The attraction between argon atoms stems from "dispersion interactions" between electrons, since the movements of the electrons of an atom affect the motions of their partner's electrons. DFT can not correctly explain these correlated movements over a long distance.

And that's a problem, especially in an area such as materials science, where physicists can design and predict the properties of a new material – from its strength to its magnetism its ability to conduct heat – without ever going to a lab to do an experiment.

So in the early 2000s, physicists began to develop "fudge factors" to explain this dispersion energy. Some of these methods turned out to be relatively good results and became an extremely popular tool in computer physics, chemistry and materials science. The scientific papers suggesting such methods have been cited tens of thousands of times.

What Shahbaz and Szalewicz have shown after more than a year of intense analysis is that all these wrong methods are actually based on a misconception. DFT can describe how the motion of one electron affects and influences the motion of another electron when the distance between them is on the order of one angstrom. For separations above 1 angstrom to about 7 angstroms, the correction techniques assume that the DFT recovers a fraction of these effects. Shahbaz and Szalewicz have found that this size does not have the characteristics of dispersion energy and is actually due to errors in theory that are not related to dispersion. So the researchers say the correction methods could get good results, but for the wrong reasons.

"We tell the physics community that you need to move on to a universal method of forecasting that works for the right reasons," says Shahbaz. "We are not here to criticize but to improve," he humbly adds.

Currently, Szalewicz and Shahbaz belong to a team of theoreticians and experimentalists from universities in the United States who use quantum physics to predict the structures and behavior of the energies of crystals that make up snowflakes, ice, most rocks and minerals , some plastics, pharmaceuticals, energetic material and other products are manufactured. For example, their complex calculations predict how much energy can be packed into a given amount of rocket fuel.

Shahbaz, the first author of the journal article, says he never knew in his small village as a child in Pakistan that one day he would become a physics professor. He grew up and helped his father, who is a farmer, grow reeds, chilies, tomatoes, eggplants, radishes and okra. Now he's the first in his family to have a university diploma, not to mention the highest academic degree in sight.

When he enrolled at the Graduate School, he received offers from universities in the US and Canada, but he says he ultimately chose UD because of the University's reputation and the flexibility to first do a Master's. He says that helped him to decide what he really wanted to focus his research on.

If he does his doctorate in the next few months, he already has a job as assistant professor of physics at the University of Punjab in Lahore, where he should teach students how light and gravity work, as he was fascinated as a teenager.

Why does he like physics so much?

"Physics says something about the laws of nature, says Shahbaz." It also requires a justification. You do not have to memorize anything – just take your life.

This work was supported by the US Army Research Laboratory, the Army Research Office, and the National Science Foundation.


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