The Periodic Table

1:39 AM

@orthocresol oh then that's great!

Q: If you put effort into answering a question, it's probably worth an upvote

2:01 AM

chemistry.stackexchange.com/q/93983/5026 i'm surprised four people answered this question, but none upvoted it, reminds me of

I've started thinking that our site's users need to be a little bit more generous long before, but after this Question about the best loser from a new user gathered 5 answers and only 1 upvote (by the time of publishing) I got really upset. This issue was already discussed in other communities a...

(coincidentally it happens to be my own question in this case, but am definitely not asking for upvotes, this is a general remark)

2:14 AM

@Mithoron "Probably more important process is loss of energy as heat" but does that heat loss happen after the pumping is over, or during the pumping is being done?

7 hours later…

9:28 AM

@Loong, is there a symbol for a dimensionless version of Avogadro's number?

@orthocresol Hm, both $N_\mathrm A$ as well as $L$ are used for the Avogadro constant (i.e. 6E23 mol^{-1}), but there seems to be no current symbol for the historical dimensionless Avogadro’s number.

10:15 AM

@BalarkaSen The Worldbuilding main site is already chatty enough.

10:43 AM

@Loong is it written Q_c or Q_\mathrm c? You changed the latter to former, why? Why's it different from the notation for the acid dissociation constant?

1 hour later…

MollyCooL

12:08 PM

Guys! What are all the prefixed links do we have? Eg: [tour]

MollyCooL

12:31 PM

Any1 alive?

1 hour later…

A: Add data.SE style "magic links" to comments

1:40 PM

@GaurangTandon Yes, that’s correct. $c$ is a quantity symbol in this case.

338

Most of these now work. My comment below has the following markdown source: On [main], you are expected to write proper English (as advertised on [english.se]), but here on [meta.se] it's more important to have freehand circles, so please [edit] your post, otherwise I'll have to flag you (see...

2:09 PM

@Loong oh, got it!

Abcd

2:21 PM

test message : Chemistry Meta

MollyCooL

Thanks @Loong. Why don’t we have one for MathJax?

Abcd

test message: Ask on Chemistry not here. Please [edit] this. Hey please see what meta is about using [meta-tour]. Please How to Ask this question

Learn How to Answer

3:22 PM

@pentavalentcarbon you're familiar with McMurchie-Davidson scheme, right?

M.A.R. ಠ_ಠ

@Loong c00ll33t

@Abcd nor everything that works in comments works in chat

Q: Why don't we explode after drinking water?

4:13 PM

@Loong Thanks, I was just wondering, because sometimes I see things like "1 mole of hydrogen atoms, or N_A atoms of hydrogen".

Behold, our latest HNQ:

It is known that acid should be added to water and not the opposite because it results in an exothermic reaction. Our stomach contains HCl, so why don't we explode when we drink water?

acid-base everyday-chemistry water

@orthocresol I was just trying to calculate something for that.

I'm not impressed with this one... you may convince me otherwise

I probably cannot.

@orthocresol Yeah, I also often stumble upon things like "n moles". :-(

chemistry.stackexchange.com/search?q=%22n+moles%22

4:50 PM

So like as in unsaturated compounds, in alicyclic compounds, the higher sum of locant structure is the correct one — Jayanth Bala 39 mins ago

no, no, no, and no

maybe I miscounted

5:09 PM

I had no idea how to reply to that, so I simply didn't.

Maybe I should change that stock comment to "does not exist" instead of "is incorrect".

@orthocresol these clickbait titles do come up a few times...

5:41 PM

@orthocresol Hm, yeah, it's hard to kill: chemistry.stackexchange.com/a/54112/7951

M.A.R. ಠ_ಠ

6:01 PM

@orthocresol FFS

I. Am. Ashamed

6:13 PM

@obackhouse I haven't implemented it, only Obara-Saika, but I've read the paper...so maybe.

Ah OK, maybe won't know then. I was wondering if anyone achieved an implementation which used explicit functions for the expansion coefficients rather than recursion/loops

I'm trying to experiment with it in my code, my thought was that the conditional statements in typical implementations slow it down a lot

6:29 PM

That I definitely couldn't tell you. I just looked at the MD code I know about, and that isn't done

But that's an interesting thought. Simple conditional operations should have dedicated machine instructions, so they should be relatively fast, faster than a single floating-point operation

I managed and I didn't notice any difference in time for sto-3g water.. my suspicion is that the benefit will only be noticed when the basis set has functions with higher angular momenta

My knowledge of computer programming is very weak so I don't have any room to speak about optimizing this sort of thing, though

I know a lot of the practical settings which used MD schemes calculate all of the expansion coefficients before computing any molecular integrals, because many are calculated multiple times otherwise

But that is seriously hell to organise and I don't see it being efficient memory-wise for larger systems

6:46 PM

What language are you writing this in?

Anything like an interpolation table will be precomputed or hard-coded

I can tell you that PRISM uses a giant array to store all those intermediates with some indexing scheme to avoid recomputation

C++

Ok, then I'd expect the effect of optimizations to be clearer, because you don't have the extra layer of obfuscation by the interpreter (Python)