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Topic: Relativistic effects in quantum chemistry  (Read 2817 times)

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Offline Shadow

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Relativistic effects in quantum chemistry
« on: September 25, 2014, 05:16:00 AM »
I see that relativistic effects explain many important things. When do relativistic effects appear in the periodic system, why and how?

Offline Corribus

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Re: Relativistic effects in quantum chemistry
« Reply #1 on: September 25, 2014, 09:44:15 AM »
Generally not until the late transition metals. A common explanation for why relativistic effects occur at very high Z numbers is that when the nuclear core charge increases, so too does the average speed of orbiting electrons because the Coulombic force magnitude becomes large. At some point the electronic speed is sufficiently close to the speed of light that relativistic effects can no longer be ignored. Be aware that there's no hard and fast cut-off for when this happens. Relativistic effects are treated as a perturbation, and they could be applied even in hydrogen if you wanted to. The effects are not great enough to observe really until about period six, in elements like mercury and gold.
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Offline Shadow

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Re: Relativistic effects in quantum chemistry
« Reply #2 on: September 25, 2014, 09:58:15 AM »
What equation describes that?

Offline Corribus

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Re: Relativistic effects in quantum chemistry
« Reply #3 on: September 25, 2014, 10:33:08 AM »
Not everything can be described by a simple equation. You can probably find a textbook on relativistic quantum mechanics if you're really interested. Or you can start here: http://en.wikipedia.org/wiki/Relativistic_quantum_mechanics. I wish you luck. :)
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Irlanur

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Re: Relativistic effects in quantum chemistry
« Reply #4 on: September 25, 2014, 05:09:42 PM »
first thing: "relativistic effect" is a really strange term because it means "everything we cannot describe by the schrödinger equation but need the DIRAC EQUATION". so it's a completely theoretical term.


Offline Irlanur

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Re: Relativistic effects in quantum chemistry
« Reply #5 on: September 25, 2014, 05:10:59 PM »
also spin emerges naturally from the relativistic treatment of the electron.

Offline Mitch

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Re: Relativistic effects in quantum chemistry
« Reply #6 on: September 25, 2014, 07:09:58 PM »
This paper from Pitzer is a good beginning place to begin on this topic. I highly recommend it and it was a reference I used in my thesis.

Relativistic effects on chemical properties by Kenneth S. Pitzer Acc. Chem. Res., 1979, 12 , pp 271–276.
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Offline Corribus

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Re: Relativistic effects in quantum chemistry
« Reply #7 on: September 26, 2014, 10:33:34 AM »
Mitch,
That's a great article. I read it first sentence to last. Thanks for sharing it.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Mitch

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Re: Relativistic effects in quantum chemistry
« Reply #8 on: September 28, 2014, 12:59:45 AM »
I'm glad you like it.
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