> physics that predicts chemistry

Do we have this?

gus_massa 6 hours ago | parent | next [-]

Yes but ... after a few not so mild assumptions, it takes exponential time to solve it. In this case, you need 6 electrons in 2x5 orbitals for the Carbon and 82 electrons and 2x43 orbitals for Bismuth- (perhaps more, I usually work with lighter atom). So now the free parameter are Combinatoric(96,88)~=3E13 and you must construct a matrix of [3E13 x 3E13] and then find the minimal eigenvalue. So you must make a lot of simplifications and more assumptions to get the result before the universe dies.

And this is for a very cold isolated molecule like in this experiment. If you have many moving molecules surrounded by a lot of water molecules at a usual room temperature, it gets much much much worse.

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jandrewrogers an hour ago | parent | prev | next [-]

More or less, but it is profoundly computationally intractable even in relatively trivial cases. Trying to do this was one of the earliest use cases for supercomputers. It is genuinely a “boiling the ocean” type problem.

Practical attempts use a lot of heuristics and approximations, which risks fidelity.

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marcosdumay 6 hours ago | parent | prev [-]

You know that people simulate chemistry on computers, right?

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JumpCrisscross 6 hours ago | parent [-]

Yes. We also simulate cosmology and quantum systems and play Sims.

	▲	marcosdumay 5 hours ago \| parent [-]
		The difference being that the chemical simulations get the correct answers on most conditions. And probably the few they miss are because of the simulation limitations, not of the underlying model. Those other simulators aren't there to tell you the result. Instead people put the result in to find how the simulation behaves in cosmology, and don't care about them in Sims.