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Einstein's relativity rules chemical bonds in heavy elements, new research shows

brown.edu

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Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#101

Post by rramadass »

nomel wrote: post #7
aaaronic wrote: post #5

Earlier quoted context omitted.

Sigma and Pi bonds are typically covered in AP Chemistry, even if the “why/how” is hand waved pretty heavily. The valence cloud shapes get wild for heavier atoms and bonds between two or more atoms add even more to the mix.

I had incredible difficulties with Chemistry, more than any other subject, because most everything was hand waved away, requiring mostly rote memorization. I could never get an intuitive understanding, partly because my profs seemingly refusing to think about things from a physics perspective. My physics prof was able to help with some of it. It was very odd. If I would have stuck with it, would things have improved?

> If I would have stuck with it, would things have improved?

Yes.

I have a B.Sc in Chemistry (Honours) from late 1980s and it was not until the final year that things finally began to click. The main catalysts were the books "Concise Inorganic Chemistry by J.D.Lee" and "Mechanism in Organic Chemistry by Peter Sykes". Both beautifully written and try to give a framework within which to think viz. the former based on the periodic table and the latter on carbon valence bond properties. I think i need to revisit these (and other books) to justify my degree in Chemistry :-)

For background and inspiration, consult Linus Pauling's classics; The Nature of the Chemical Bond and General Chemistry - https://archive.org/search?query=creator%3A%22Pauling+Linus%...

Linus Pauling (the only scientist in history to be awarded two undivided, unshared Nobel Prizes) - https://en.wikipedia.org/wiki/Linus_Pauling

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#102

Post by smj-edison »

not-a-llm wrote: post #98
smj-edison wrote: post #69

Earlier quoted context omitted.

Depends what level of accuracy you want. I just started in a computational chemistry lab so I'll probably get some details wrong, but for small systems, you can use a method called CCSD(T) for up to ~20 atoms, but it scales O(N^7). I've been mainly using DFT for the systems I've been simulating, which scales O(N^3). I've been running a system with about 50 atoms with a decent basis set (how the orbitals are modelled)…

do you think quantum computers would help simulating this? I've seen contradictory opinions from the experts - it can in theory but not really in practice (even assuming sufficiently large quantum computers will be built)

I'm only a freshman, so I don't feel very qualified to comment on that :) I hope so though!

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#103

Post by smj-edison »

vessenes wrote: post #92
smj-edison wrote: post #69

Earlier quoted context omitted.

Depends what level of accuracy you want. I just started in a computational chemistry lab so I'll probably get some details wrong, but for small systems, you can use a method called CCSD(T) for up to ~20 atoms, but it scales O(N^7). I've been mainly using DFT for the systems I've been simulating, which scales O(N^3). I've been running a system with about 50 atoms with a decent basis set (how the orbitals are modelled)…

Cool details, thanks. To help me understand your life, what would be like a one year and a five year research goal for you? I never spent time in lab sciences so it’s kind of a black box for me.

Disclaimer: I'm only a freshman, so there's still a ton I don't know :)

Right now the lab is having me get comfortable using software like Gaussian and ORCA by simulating a bifurcating reaction. This is a reaction that, depending on the catalyst's momentum, will change what site it bonds to (it makes either a 6-membered or 7-membered ring). I'm finding the intermediate states (where the molecule is most stable) and transition states (the tipping point), and then running trajectories to see which output is more likely.

Once I've finished simulating that, I should be comfortable enough with the process to jump on the bigger project, which is machine learning interatomic potential (MLIP) model distillation. There's a lot of exciting work around speeding up DFT methods by using machine learning (note this is not generative AI, it's merely predicting the molecule energy based on atomic positions). So my one year goal is to get on that project and start contributing.

My five year goal is to, well, graduate. But then I'll probably do a PhD in computational chemistry, since I'm really interested in ways to speed up and scale existing methods. My big dream is to simulate large biological systems while still having bond formation and breaking, to automatically elucidate biochemical pathways, but there's still a lot of steps in-between.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#105

Post by [deleted] »

nomel wrote: post #7
aaaronic wrote: post #5

Earlier quoted context omitted.

Sigma and Pi bonds are typically covered in AP Chemistry, even if the “why/how” is hand waved pretty heavily. The valence cloud shapes get wild for heavier atoms and bonds between two or more atoms add even more to the mix.

I had incredible difficulties with Chemistry, more than any other subject, because most everything was hand waved away, requiring mostly rote memorization. I could never get an intuitive understanding, partly because my profs seemingly refusing to think about things from a physics perspective. My physics prof was able to help with some of it. It was very odd. If I would have stuck with it, would things have improved?

[deleted]

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#107

Post by aduty »

nomel wrote: post #7
aaaronic wrote: post #5

Earlier quoted context omitted.

Sigma and Pi bonds are typically covered in AP Chemistry, even if the “why/how” is hand waved pretty heavily. The valence cloud shapes get wild for heavier atoms and bonds between two or more atoms add even more to the mix.

I had incredible difficulties with Chemistry, more than any other subject, because most everything was hand waved away, requiring mostly rote memorization. I could never get an intuitive understanding, partly because my profs seemingly refusing to think about things from a physics perspective. My physics prof was able to help with some of it. It was very odd. If I would have stuck with it, would things have improved?

No.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#108

Post by fsloth »

Diogenesian wrote: post #17
nanolith wrote: post #14

Wait... wasn't it already understood that relativity influences electron orbits of heavy elements? I clearly remember being taught some of this in physics, in the mid-noughties. For instance, we know that gold gets its color from relativistic effects. https://physics.aps.org/articles/v10/s3

Seems to be the first time this was confirmed via direct experimental observation of the orbitals: “This idea that relativity is important in heavy elements has been around since the 1970s,” said Lai-Sheng Wang, a professor of chemistry at Brown and the study’s corresponding author. “But we show direct spectroscopic evidence that what we learned in high school about chemical bonding isn’t true in heavy elements."

I came to the comments exactly for this ("wait I thought we 'knew' this already").

I'm so happy we have HN with likeminded people and no noise.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#109

Post by pmarreck »

nomel wrote: post #7
aaaronic wrote: post #5

Earlier quoted context omitted.

Sigma and Pi bonds are typically covered in AP Chemistry, even if the “why/how” is hand waved pretty heavily. The valence cloud shapes get wild for heavier atoms and bonds between two or more atoms add even more to the mix.

I had incredible difficulties with Chemistry, more than any other subject, because most everything was hand waved away, requiring mostly rote memorization. I could never get an intuitive understanding, partly because my profs seemingly refusing to think about things from a physics perspective. My physics prof was able to help with some of it. It was very odd. If I would have stuck with it, would things have improved?

I had the same issue! I absolutely destroyed AP Physics (first person in the history of the school to get a 5 on the AP and 100 on the NYS Regents) but got a D in AP Chem one semester, my lowest grade ever!!
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