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seen Dec 16 at 23:10

Sep
19
accepted Bond Angles - H2O vs CO2
Sep
16
comment Bond Angles - H2O vs CO2
@Wildcat In the Born-Oppenheimer (or Car-Parrinello) approximation, does a single SiO2 molecule come out as linear? And, is a single SiO2 molecule truly linear? I know that most SiO2 is bulk silica which changes everything, but wondering if the ball-stick model still works for a single SiO2 molecule (which would be equivalent to a CO2 molecule though Si's ball is bigger).
Sep
16
awarded  Curious
Sep
16
revised Bond Angles - H2O vs CO2
added 108 characters in body
Sep
16
comment Bond Angles - H2O vs CO2
@mikhailcazi It's amazing that a simple tetrahedral ball-stick model (representing sp3 orbitals) gives nearly the exact bond angles for both molecules though the true multi-electron Schrodinger equation is so complicated! I can't think of a better success in QM simplification. Since you didn't submit an answer, I can't give you answer credit, but your comment helped me the most.
Sep
14
comment Bond Angles - H2O vs CO2
In your terms, my question is how do we know theoretically that CO2 belongs to D∞h? Within the "filled-shells model", one could position 3 nuclei (with charges +6, +4, and +6) and apply the many-bodied Schrodinger equation to 16 electrons...then find the nuclei positions which have the lowest energy...but that problem is too difficult for current computers. mikhailcazi's comment actually answers my question for why CO2 should be more linear than H2O, but I suspect that perfect linearity has never been theoretically proven. Has it?
Sep
13
asked Bond Angles - H2O vs CO2
Jul
1
awarded  Popular Question
Oct
14
awarded  Critic
Oct
14
comment Why do tsunami waves begin with the water flowing away from shore?
This isn't seen in small-scale wave tank experiments and is therefore hard to believe. Is there even a simulation on the web showing significant recession from a positive pressure source like you describe? I like the simpler answer from Carlos more (it is surprising that most earthquakes would lower the ocean floor, but I guess it would make sense that the earth tends to stabilize into a more compact form).
Sep
7
comment Conservation Laws in Photon Parametric Down-Conversion
No matter what kp, ks, and ki you choose (by "example", I wanted some actual numbers), I don't think that you can conserve both energy and momentum. Instead, I think Ron Maimon is correct in his comment above. So, I'd say Wikipedia is wrong (in answer to my original question) and "parametric" is not used/defined well here.
Jul
20
awarded  Yearling
Jun
11
comment Atmospheric Circulation
If I'm skimming that paper correctly, their constructal model doesn't predict a single cell for >144h rotation periods (they just give references to other papers showing it), right?
Feb
25
comment Induction cooker + superconductive pot
At first, it will start to levitate. But, it will soon tilt due to a misbalance and then accelerate this tilt...the 3D shape of the superconductor will then determine how the induced currents flow. Of the three options you gave, I'd say "tremble".
Feb
23
answered Induction cooker + superconductive pot
Jan
9
comment Atmospheric Circulation
Thanks, good link. I get it now, but now would think that even a non-rotating earth could have multiple convection cells. So, I feel like simulation is always needed and there's no hope for the "justifiable formula" I asked for. For the simulator, it seems I need to add another parameter for the air's thermal radiation back into space.
Jan
7
comment Atmospheric Circulation
It's hard for me to understand how the vertical gradient could amplify circulation, so perhaps someone could simply show an airflow simulation for a non-rotating planet with one circulation cell? It seems to me that cooling of the upper atmosphere around the equator would actually slow circulation...but it's all quite complicated, especially modeling the thermal diffusion/convection within the air. Since there's not much interest in this question, I wonder if someone could just give a quantifiable explanation of the Ferrel cell; why would hot "south air" flow under cold "north air"?
Jan
2
asked Atmospheric Circulation
Sep
13
comment Dimension analysis of de Broglie equations
by the way, your p has incorrect units (you should only have first power for m and s)
Sep
13
answered Dimension analysis of de Broglie equations