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Martin - マーチン
Martin - マーチン
5:22 AM
@Secret If it has a crystal structure it is more stable than many other compounds...
I had a reason to check chat... then I came here and forgot *sigh*
 
 
4 hours later…
M.A.R.
M.A.R.
9:29 AM
@Secret Oh crap
 
DHMO
DHMO
10:05 AM
How does this work? Why particularly that hydrogen is substituted by a bromine atom?
 
 
3 hours later…
user228700
1:35 PM
@paracresol Ah, The Invisible Man, eh?
 
DHMO
DHMO
$\ce{CH3COOH ->[1. \ce{PCl3}][2. \ce{CH3OH}] CH3COOCH3}$
 
paracresol
paracresol
@Kaumudi.H Crap, you're alive...
 
user228700
@paracresol Was there reason to believe that I may have died at any point of time?
 
paracresol
paracresol
^ No, that was just me being optimistic ;D
 
user228700
@paracresol I see. I was going to offer a "tip" (of sorts) for the boards but I've changed my mind--after all, you were hoping that I'd have died.
 
paracresol
paracresol
1:38 PM
Um...okay ._.
 
DHMO
DHMO
@paracresol could you help me?
 
user228700
@paracresol Just curious, BTW, how is your English so good? I didn't think (I did have reason to believe this) that Malayalis' (by which I mean those living in Kerala) English was any good (Well, that does seem like gross generalisation but still...)
 
paracresol
paracresol
^^ Herr Wassermann you know that I'm not the man for that :/ (At any rate, I'm going to leave in a minute or two) Sorry bud.
 
DHMO
DHMO
alright
 
paracresol
paracresol
@Kaumudi.H Flattered =*_*=
 
DHMO
DHMO
1:43 PM
ich bin nicht einer Wassermann :p
 
user228700
@paracresol I'm sorry, I didn't mean to offend you.
 
paracresol
paracresol
@DHMO ^ You are :3
 
user228700
@Para: Oh, when are ur boards ending, BTW?
 
DHMO
DHMO
Basketane
Basketane is a polycyclic alkane with the chemical formula C10H12. The name is taken from its structural similarity to a basket shape. Basketane was first synthesized in 1966, independently by Masamune and Dauben and Whalen. == See also == Cubane 8-Aminopentacyclo class of 'Polycyclic cage molecules' == References == == Further reading == Binmore, Gavin T.; Della, Ernest W.; Elsey, G. M.; Head, N. J.; Walton, J. C. (1994). "Homolytic Reactions of Homocubane and Basketane: Rearrangement of the 9-Basketyl Radical by Multiple β-Scissions". J. Am. Chem. Soc. 116 (7): 2759–2766. doi:10.102...
 
paracresol
paracresol
@Kaumudi.H Why don't you account for your proficiency first?
 
user228700
1:45 PM
@paracresol Well, Chennai is a lot different from...Pathanamthitta.
 
paracresol
paracresol
@Kaumudi.H April
5th
 
user228700
Bummer.
 
paracresol
paracresol
Nah
We, get a decent gap for Bio...
 
DHMO
DHMO
@paracresol have a look here synarchive.com/syn/100
 
paracresol
paracresol
10 days
 
user228700
1:45 PM
Why not..? Oh, thaan Bio analle?
 
paracresol
paracresol
Woohoo \o/
 
user228700
@paracresol Nice. We had about 2 weeks for C.S last year--it's actually not that great but then again, C.S is too easy compared to Bio.
 
paracresol
paracresol
@Kaumudi.H I know that -_-
 
Martin - マーチン
Martin - マーチン
 
paracresol
paracresol
@Mart o/
 
Martin - マーチン
Martin - マーチン
1:50 PM
aha...
hi!
 
paracresol
paracresol
@DHMO Whoa!!! And more than half of those are reactions we've learnt! Thanks!
Hallo Mart!
 
DHMO
DHMO
@paracresol lol
@Martin-マーチン Could you help me?
 
paracresol
paracresol
^^ O_o
 
Martin - マーチン
Martin - マーチン
@DHMO i have little time right now, but go ahead
 
DHMO
DHMO
How does this work? Why particularly that hydrogen is substituted by a bromine atom?
 
paracresol
paracresol
1:52 PM
^ Can't see ._.
 
user228700
^ Maybe you're blind ._.
 
paracresol
paracresol
Oh wait, I can after I've clicked it :D
 
Martin - マーチン
Martin - マーチン
 
user228700
Bye, guys.
 
Martin - マーチン
Martin - マーチン
alylic protons can easily be abstracted by radicals, because the resulting radical is resonance stabilised
 
paracresol
paracresol
1:56 PM
@Kaumudi.H o/
Um...@Mart, how much University physics do you still remember?
 
Martin - マーチン
Martin - マーチン
@paracresol none
 
paracresol
paracresol
Can I star that^
@Martin-マーチン How about mechanics? Hamiltonian?
 
Martin - マーチン
Martin - マーチン
bits and pieces maybe, but before answering any questions, I'd rather look it up again...
 
paracresol
paracresol
@Martin-マーチン Can we continue talking in the other room?
 
Martin - マーチン
Martin - マーチン
no i can't. I need to leave, they are locking up in a couple of minutes
 
paracresol
paracresol
2:03 PM
@Martin-マーチン Whup, sorry...how about tomorrow?
 
Martin - マーチン
Martin - マーチン
maybe monday... I go offline for most of the weekend
 
paracresol
paracresol
@Martin-マーチン Danke I'll ping you then!
@hBy2Py You could put that up as an answer, you know. On my part, I could even accept it 3;D
6
Q: Mercury metal: Not toxic?

paracresolNow I (and most of us here, I guess) have grown up around "Mercury's toxic! Avoid handling it! Do NOT screw around with this thing, if you love your life" and other equally heartening pieces of advice regarding mercury. Apparently mercury poisoning makes you, really lose it. https://en.wikipedia....

everyday-chemistry metal toxicity
 
DHMO
DHMO
@Martin-マーチン Thanks, but I still don't understand why particularly those around the double bond are substituted
 
Mithoron
Mithoron
@DHMO Because it's radical mechanism?
 
DHMO
DHMO
Could you elaborate?
 
Mithoron
Mithoron
2:14 PM
One radical removes allilic hydrogen and from resulting radical bromide is created.
 
DHMO
DHMO
What is so special about allylic hydrogens?
 
Mithoron
Mithoron
21 mins ago, by Martin - マーチン
alylic protons can easily be abstracted by radicals, because the resulting radical is resonance stabilised
 
DHMO
DHMO
Oh, thanks
 
DHMO
DHMO
2:36 PM
What is the peak at m/z = 27?
it has to be C2H3 of course, but what is that?
 
Mithoron
Mithoron
2:48 PM
@DHMO Protonated acetylene
 
DHMO
DHMO
@Mithoron stabilized by what?
So $\ce{Me3CH+ -> C2H3+ + CH3 + CH2}$...
 
Bounty Hunter
Bounty Hunter
0
Q: How to determine whether a organic compound is diamagnetic or not?

anilineI have faced several questions regarding the diamagnetic behaviour of certain organic compounds. I know that one has to check the electronic configuration of the atoms in the compound and see if there is an unpaired electron or not? Of all aromatic compounds (benzene, cyclopropene cation, cyclope...

organic-chemistry
 
Mithoron
Mithoron
@DHMO It isn't particularly stable IMO. And you don't see neutral fragments so...
 
DHMO
DHMO
@Mithoron could you explain how it is formed? I don't see any viable mechanism...
 
Mithoron
Mithoron
In MS molecules have so much energy they break apart. There are some mechanisms but aren't terribly important
 
DHMO
DHMO
3:02 PM
What I mean is that I cannot see any mechanism that does not involve the hydrogen radical, which should be impossible...
 
Mithoron
Mithoron
What? Atomic hydrogen? That's pretty obvious it leaves in one path, with creation of t-butyl. There's no problem with that. H is like most stable thing there as it can't break apart.
 
DHMO
DHMO
you don't exactly see a peak at 57 (t-Bu+)...
 
Mithoron
Mithoron
@DHMO There is a small one as t-but still has excess energy
 
DHMO
DHMO
I see...
 
Mithoron
Mithoron
MS isn't like chemistry in mixture, rather in hard vacuum and radiation
 
DHMO
DHMO
3:15 PM
Why is protection of carbonyl group needed?
 
Mithoron
Mithoron
Bye
 
hBy2Py
hBy2Py
@paracresol I don't think I even knew this question existed...!
 
hBy2Py
hBy2Py
3:51 PM
Answer posted; not sure if it adds enough past matt_black's answer to merit a switch of the checkmark, though.
 
M.A.R.
M.A.R.
4:17 PM
Not sure if you've seen this or not
-12
Q: How much I have to wait for my question to be answered?

dr. honeyWhy there is no equilibrium attained in open system when we have infinite amount of matter out there? This question I asked 16 hrs ago and no one not a single person have answered it. This is for first time the delay thats why I am asking?

support unanswered-questions
The first thing that relates specifically to our site on the mother meta after like a decade and this is what it looks like.
Facepalm
 
hBy2Py
hBy2Py
4:45 PM
@M.A.R. At least they were, overall, pretty gentle.
I expect a lot of newer askers are impatient. At least this one seems not to be a HALP PLZ HAV HMRWK case.
Several other pretty good questions in the network.
 
M.A.R.
M.A.R.
Yah they're just curious
 
hBy2Py
hBy2Py
 
M.A.R.
M.A.R.
As I said, a curious observer
 
hBy2Py
hBy2Py
<nod>
 
M.A.R.
M.A.R.
I used to call those guys Aristotles
26
Q: Why is the color of lightning white or blue rather than nothing?

dr. honeyAccording to my knowledge, when clouds get charged, they produce sparks, which look like lightning to us. My question is, why does lightning have a color? It consists of electrons, and should not radiate light. If it radiates light after hitting air particles, then it should radiate only X-rays. ...

visible-light electromagnetic-radiation thermal-radiation lightning
What does something of no color look like?
 
hBy2Py
hBy2Py
4:53 PM
Transparent, I guess.
He's probably thinking of color from a 'crayons' perspective, where "white" is a separate color.
 
M.A.R.
M.A.R.
Arguably, and philosophically, even transparent stuff is the color of what's behind it
 
hBy2Py
hBy2Py
Ennnnnnggh, I'd need convincing of that.
Transparent materials are to color like dividing by zero is to math: undefined.
 
M.A.R.
M.A.R.
Color is our perception, not what's really there.
I mean it's not absolute.
 
hBy2Py
hBy2Py
But that would mean that two observers at different angles might declare the same transparent substance has having two different colors at the same time.
Ultimately, if anything, it breaks the simplistic model of "a thing has a color"
 
M.A.R.
M.A.R.
If your mind couldn't process and tell you there's a distance between the glass and what's behind it, you wouldn't see them as different things
@hBy2Py Well yeah
 
hBy2Py
hBy2Py
4:56 PM
I see where you're arguing from; I disagree with you about it, though. :-)
 
M.A.R.
M.A.R.
If it's got to be relative, then let it be relative
And well, even non-transparent things don't have the same color for all of us
So it's ''for each person, at a certain time and location, a thing has a color''
This is accurate
 
gannex
gannex
honestly if you messed with your wifi firmware, you should've been able to make it seamless enough that the houseguest couldn't figure it out unless they went to 192.168.1.1
<3 xkcd
@M.A.R. On the topic of colour perception:
"Let us take first the simpler case of monochromatic vision. Suppose it is suggested that someone might be a physical dupliucate of me, but see as fark what I see as light, and vice versa. Is that possible? Our snap judgement might be that it is. Perhaps we imiagine the world appearing to him as it appears in a photographic negative. But this does not really work. If I make a piece of grey glass lighter, I see better through it; if I make it darker, I see less well through it. Since he is a physical duplicate, this has to be true of my twin. But fo…
 
hBy2Py
hBy2Py
5:14 PM
Oops. Responded w/o checking who actually posted... >.<
 
gannex
gannex
I was talking about the philosophy that happens at the subjective level, after the objective phenomenon of long, medium, and short cones.
obviously the physical interactions are objective, but philosophy becomes a better tool than science for answering the question "do we all see the same-looking stuff?" after the initial interactions of light with retinal cells. Very good book, Think.
 
hBy2Py
hBy2Py
Yeah, color perception is quite the rabbit hole to explore.
 
gannex
gannex
If we had a little bit of a better understanding of the physicality of qualitative experience, we could use science here, but the problem is that science is empirical and therefore it cannot really probe the noumenal things, like qualitative experience. "Science cannot solve the ultimate mystery of nature, for in the final analysis we ourselves are part of the mystery we are trying to solve." -Max Planxk
we can't get outside of ourselves.
(usually)
Planck*
 
M.A.R.
M.A.R.
@gannex The smallest drift from absolute objectivity means it's strictly not objective
@gannex Are you on mobile?
 
gannex
gannex
@M.A.R. OK but think out the duplicate thought experiment. It doesn't make much sense that your "twin" could have a different subjective colour perception experience from you.
Now, this doesn't really tell us about other people who are not hypothetical duplicates, for, as we know, some women are tetrachromats, and they certainly have a different experience. But if a duplicate could not have a different colour perception, it seems reasonable that another person (barring mutation) should also experience the same colours as you.
@M.A.R. No, I'm on my laptop.
why?
 
M.A.R.
M.A.R.
5:25 PM
@hBy2Py Well yeah, I'm delving into philosophy rather than hardcore science
 
gannex
gannex
beyond the point of retinal cells, philosophy becomes a more useful instrument than science for answering this question (see max planck quote)
 
M.A.R.
M.A.R.
I don't think we disagree on the little amount of science we know about colors
@gannex Nothing, it seemed you were fighting a fat finger
Unless you're Goliath or something
 
gannex
gannex
"fighting a fat finger"?
 
M.A.R.
M.A.R.
@gannex Yeah, trying to type in mobile with so little buttons . . .
 
gannex
gannex
...no I was typing out a paragraph from a book without looking at the screeen. I'm not perfect.
 
M.A.R.
M.A.R.
5:27 PM
Well it seemed that way.
 
hBy2Py
hBy2Py
@M.A.R. <nod>, and that's why I was in durable disagreement -- I was approaching it from the physical direction.
 
gannex
gannex
well we have nothing to argue about from the physical direction
 
M.A.R.
M.A.R.
Yeah, it's boring
 
gannex
gannex
:P
 
M.A.R.
M.A.R.
Philosophy on the other hand, is what we all can talk about and yet know nothing about
Or logic
 
gannex
gannex
5:29 PM
well, we must first define out epistemological systems. If we stick with cartesian dualism, we will never get anywhere. We need to make some concessions.
our*
 
M.A.R.
M.A.R.
!!flip/Epistemology
 
Chemobot
Chemobot
(づ๑ʖ๑)┛︵Ǝdᴉsʇǝɯoꞁoƃʎ
 
gannex
gannex
XD
if we make no concessions then we won't even know that other people are real, nevermind that they percieve the same colours as us.
 
M.A.R.
M.A.R.
Pick a random number.
 
gannex
gannex
12
can't be random though.
 
M.A.R.
M.A.R.
5:32 PM
Well, you're prolly rare.
Pick a random 4-digit number
 
gannex
gannex
5608
 
M.A.R.
M.A.R.
 
gannex
gannex
seme-related question:
does anyone know where I can get a quick refresher on the physical significance of various calculus operators?
 
hBy2Py
hBy2Py
Examples?
 
gannex
gannex
i.e.: what does second/third derivative/integral "mean" when you take it of something
 
hBy2Py
hBy2Py
5:40 PM
Ahhk.
 
gannex
gannex
I'm doing some classical physics, which I haven't looked at in a while, and my calculus is bad.
I feel like engineers know this stuff, but I don't.
 
hBy2Py
hBy2Py
Multivariate operators, too? (gradient, Laplacian, divergence, curl, etc.)
 
gannex
gannex
yeah... what exactly does gradient mean physically?
 
M.A.R.
M.A.R.
The normal me would leave a snarky link to wikipedia.com, but since I'm interested too, I digress
 
gannex
gannex
I know what it is mathematically... but I need quick interpretations of physical significance of formulae
 
hBy2Py
hBy2Py
5:41 PM
In 1-D:
1st derivative is slope, rate of change; how fast a thing is
 
M.A.R.
M.A.R.
Second is how fast its fastness is
 
hBy2Py
hBy2Py
2nd derivative is curvature, rate of change of the rate: toward which direction is the rate changing
3rd derivative is "jerk", rate of change of curvature; it's the smoothness of the change
Think steering wheel and turning rate of a car
$\theta$ is the angle the car is pointing
$\phi$ is the angle of the steering wheel
which is proportional to $\mathrm d \theta \over \mathrm d t$
${\mathrm d ^2 \theta \over \mathrm d t^2} = {\mathrm d \phi \over\mathrm d t}$ is the acceleration of the direction the car is pointing -- how quickly the rate of turn is changing, and in which direction.
 
gannex
gannex
I understood the first part... that helps.
what is the gradient?
 
hBy2Py
hBy2Py
${\mathrm d ^3 \theta \over \mathrm d t^2} = {\mathrm d ^2 \phi \over\mathrm d t^2}$ is how quick the change is, of the acceleration of the direction the car is pointing -- if the jerk is large, it's like when you suddenly yank the steering wheel to one side.
The quick change from a steering wheel at rest to a moving steering wheel (large transient $\mathrm d^2 \phi \over \mathrm d t^2$) leads to people being slewed about in their seats.
The gradient points in the direction of fastest increase.
Testing ... $\nabla\Theta$
 
gannex
gannex
I don't think the math formulae are working properly for me
Do I have to turn something on?
 
hBy2Py
hBy2Py
5:53 PM
yep. Follow @Mart's instructions here:
6
A: MathJax in chat (ChatJax offshoot)

Martin - マーチンBased on the same principle, this little bookmarklet loads cancel in addition to mhchem: javascript:(function(){if(window.MathJax===undefined){var%20script%20=%20document.createElement(%22script%22);script.type%20=%20%22text/javascript%22;script.src%20=%20%22http://cdn.mathjax.org/mathjax/latest...

 
M.A.R.
M.A.R.
@hBy2Py Works for me
I mean after turning ChatJax on
 
hBy2Py
hBy2Py
The Laplacian, $\nabla\cdot\nabla\Theta \equiv\nabla^2\Theta$, is a measure of the local net curvature of a variable. At a local minimum $\nabla^2\Theta > 0$ strictly; at a local maximum $\nabla^2\Theta < 0$ strictly.
At other points, the value can be ~anything. One particular weird aspect is that $\nabla^2\Theta =0$ is possible even when a plot of the surface wouldn't look flat.
e.g., in two dimensions $\nabla^2\Theta = {\partial^2\Theta\over\partial x^2} + {\partial^2\Theta\over\partial y^2}$.
If ${\partial^2 \theta \over\partial x^2} = C$ and ${\partial^2 \theta \over\partial y^2} = -C$ at a certain point, then $\nabla^2\Theta = 0$ at that point, but the surface would look appreciably curved there.
 
gannex
gannex
oh ok I have to turn chatjax on
how do I do that
ok I'm gonna do it
one sec... my word just crashed after editing a big document. Fucking MicrobeSoft
 
hBy2Py
hBy2Py
The divergence, $\nabla \cdot \Theta$, is a measure of the "expandiness" or "contractiness" of a variable.
If the volume integral $\int{\int{\int{\nabla\cdot\Theta}}}$ over a region is greater than zero, then whatever $\Theta$ represents will have a tendency to "leak out" of that region.
Conversely, if the integral is less than zero, then there will be a "leaking in" tendency.
 
gannex
gannex
hmmm
OK I want to read this
so... I copy the javascript into the URL of my bookmark and open it?
 
hBy2Py
hBy2Py
6:05 PM
The curl, $\nabla\times\Theta$, gives a measure of the rotational character of the field. This is only defined in three dimensions, since the cross-product is only defined in three dimensions.
Yep, just create a new bookmark (I have mine in my bookmark bar) and copy the script text into the destination field.
 
gannex
gannex
what if I just paste it into the browser url bar?
 
hBy2Py
hBy2Py
Then when you click it, it should convert all existing and future MathJax.
 
gannex
gannex
the bookmark just opens about:blank when I click it
 
hBy2Py
hBy2Py
Which browser?
 
gannex
gannex
chrome
when I paste into URL bar I get a 404
"Your client has issued a malformed or illegal request."
no chrome? Let me try some other browserrs
 
hBy2Py
hBy2Py
6:07 PM
No, it works fine in my Chrome
 
gannex
gannex
hmm
 
hBy2Py
hBy2Py
Maybe try reloading the chat page first?
 
gannex
gannex
kk
 
hBy2Py
hBy2Py
The Hessian can be constructed from the outer product of $\nabla$ on $\Theta$, as $\nabla\nabla\Theta$. (Note this is not to my knowledge ever written as '$\nabla^2\Theta$'.)
In 2D, this gives a tensor (or matrix):
 
gannex
gannex
I'm definitely not doing this right. I need help with the mathjax before I can read your physics explanation
(sorry :/)
 
hBy2Py
hBy2Py
6:11 PM
I had trouble with it at first, too.
I can't remember what I did that made it work.
 
gannex
gannex
ohhhh
my java script is disabled
I turned it off for some sort of secruity reason
one sec...
 
hBy2Py
hBy2Py
Ah, yes, that will be significant. ;-)
 
gannex
gannex
XD
 
hBy2Py
hBy2Py
@hBy2Py $\nabla\nabla\Theta = \left[\left[ {\partial^2 \Theta\over\partial x^2}, {\partial^2 \Theta\over\partial x\partial y}\right],\left[ {\partial^2 \Theta\over\partial x\partial y}, {\partial^2 \Theta\over\partial y^2}\right]\right]$
 
gannex
gannex
nnope, still doesn't work
 
hBy2Py
hBy2Py
6:15 PM
<helpless shrug>
No idea, without being there to fiddle. :-(
 
gannex
gannex
kk I'll get this fixed then brb
 
hBy2Py
hBy2Py
Anyways, the Hessian is a convenient collection of all the different possible second derivatives you can construct for a given variable.
@hBy2Py In this above example where $\nabla^2\Theta=0$:
1) The diagonal elements of the Hessian will be nonzero
2) The trace of the Hessian, however, will be zero, as $\mathrm{tr}\,\nabla\nabla\Theta \equiv \nabla^2\Theta$.
 
M.A.R.
M.A.R.
@gannex Drag the bookmark to the top of the tab
Funny we keep having this long trail of conversation every time.
 
hBy2Py
hBy2Py
3) In most cases, the off-diagonal elements of the Hessian will be nonzero.
 
M.A.R.
M.A.R.
I think we should write a better manual
 
hBy2Py
hBy2Py
6:19 PM
Yep, it'd definitely be good to have.
 
gannex
gannex
OK
Javascript bookmarklets are working. I made a hello world one. But the ones from the page you linked me don't work.
 
hBy2Py
hBy2Py
Ok, so those are all the major multivariate spatial derivatives I know of: gradient, Laplacian, divergence‌​, curl, and Hessian.
 
gannex
gannex
my biologist friend requested a manual like this, it would definitely be helpful.
 
hBy2Py
hBy2Py
And all of them can be evaluated at any single point in the domain of $\Theta$.
fin
 
M.A.R.
M.A.R.
@gannex So ChatJax doesn't work?
 
Martin - マーチン
Martin - マーチン
6:24 PM
@gannex try the chrome extension
 
gannex
gannex
no. neither javascript bookmarklet works and I don't really know javascript so I ccan't figure out what's wrong.
@Martin-マーチン I'm trying to use your javascript
@Martin-マーチン I'll check the extension
 
M.A.R.
M.A.R.
@Martin-マーチン Go back to sleep
 
Martin - マーチン
Martin - マーチン
Lol
Blame Brian
 
gannex
gannex
@Martin-マーチン where do I get the extension?
 
Martin - マーチン
Martin - マーチン
Hang on let me check stack apps
 
gannex
gannex
6:25 PM
kk thx bro
 
hBy2Py
hBy2Py
@Martin-マーチン It's not my fault if you don't sufficiently silence your notifications!!! :-P
 
M.A.R.
M.A.R.
Perhaps
@hBy2Py Now I'm imagining him half a meter above the bed
 
Martin - マーチン
Martin - マーチン
@hBy2Py just kidding... I was playing a game on my phone while watching Star Trek
!!greet
@Chemobot ???
 
M.A.R.
M.A.R.
Who do you wanna greet?
Its argument doesn't seem to be optional
 
Loong
Loong
!!greet/@Martin-マーチン
 
Chemobot
Chemobot
6:28 PM
Welcome to The Periodic Table @Martin-マーチン! Here are our chat guidelines and it's recommended that you read them. If you want to turn Mathjax on, follow the instructions in this answer. Happy chatting!
 
Martin - マーチン
Martin - マーチン
I just wanted to see/test the message
@Loong thanks
 
gannex
gannex
installed MAthJax for chrome.... still nothing on the chat
going to try the solution from the people at the Math SE
 
M.A.R.
M.A.R.
All of them worked for me
 
Martin - マーチン
Martin - マーチン
I'm using the extension, which works well for me...
Nothing on mobile though
 
gannex
gannex
extension does nothing for me, and chrome won't run any of the bookmarklets; however, it will run javascript:alert("hello world"); as a bookmarklet...
 
Martin - マーチン
Martin - マーチン
6:36 PM
@gannex that is really strange
 
gannex
gannex
to make matters worse, word just crashed for the 5th time and corrupted my autorecovered paper and it's all gonnnnnneee
fml
I need to get away from Apple and MicrobeSoft asap.
 
Martin - マーチン
Martin - マーチン
Well, I'll take Ina's advice and get some sleep now... Good night y'all!
 
gannex
gannex
IT WORKS!!
:D
but word still raped me on two hours of work though :/
at least I can read your physics now @hBy2Py
I ended up having to use ChatJaxx++, as referenced here: http://meta.stackexchange.com/questions/97938/any-chance-of-mathjax-in-chat

(through tampermonkey)
 
hBy2Py
hBy2Py
7:06 PM
@gannex Clearly, it's not a one-size-fits-all solution. Annoying.
 
gannex
gannex
@hBy2Py
OK I read everything and took notes
let me tell you I haven't done calculus in almost 3 years and even then only differential and single variable integral calculus
a few questions:
does it matter what Θ is?
what is the difference between the "meaning" of a double integral and a triple integral?
and... I still want to better understand what the gradient means.
in more than one dimension.
but i guess I need to review partial derivatives... Anyways thanks for that impressively quickly-typed manual
I have written it down and hopefully it will be illuminated as I review my college mathematics.
 
orthocresol
orthocresol
7:22 PM
@gannex You probably want to start off with normal calculus. If you want to read about vector calculus, I've seen this book been recommended: amazon.co.uk/Div-Grad-Curl-All-That/dp/0393925161
 
gannex
gannex
@orthocresol I'm reviewing Cal1 & Cal2, but my university (probably stupidly) doesn't require cal3 for chemists, so I'm trying to figure out how to get away with just learning cursory topics from cal3 for Qchem (partial derivatives, second order diff. eqn's). I'll check out the book though.
 
orthocresol
orthocresol
Hmm, partial derivatives were very important in thermo. Perhaps less so in quantum although others will know better.
I can't remember the last time I used a second-order ODE. :)
 
gannex
gannex
@orthocresol btw... I have a compchem question: does this cursory explanation of the reason to use the GGA over the LDA make sense? : "The GGA includes a gradient of the density, which improves the accuracy of the approximation with respect to the local density approximation (LDA), which only employs the value of the density and tends to overestimate Exc."
 
orthocresol
orthocresol
I'm afraid I don't know anything about that.
 
gannex
gannex
@orthocresol my university skimmed through math in thermo and made it very easy for us, plus it was my worst subject.
my university produces useful PhD students, but nobody seems to care about the fundamentals of chemistry. I'm trying to escape.
ah ok. thx anyways. I always see your quantum chem answers, so I figured you might be into comp chem too
 
orthocresol
orthocresol
7:31 PM
Ah. Well, in my own experience, one has to strike a balance. You could learn everything from scratch if you really wanted to but there's gotta be a limit somewhere (otherwise you might as well be a physicist). Where the limit is is up to you to decide ;)
Actually, they don't even teach any comp chem here. I have no clue how people manage to get into comp chem PhD's.
So, I know what $E_{xc}$ is, but I don't actually know anything about the methods used to approximate it.
Oh well.. gotta run off... all the best with the maths!
 
gannex
gannex
@orthocresol I want a cursory understanding of the maths and physics, whatever is needed to give me enough understanding to do some QChem & know what's under the hood when doing computations.
@orthocresol aren't you at Oxford? I heard they were starting a comp. chem. program there.
 
hBy2Py
hBy2Py
@gannex No, it's an arbitrary continuous variable. The only restrictions are for the curl, where it has to be a variable in 3-D space.
@gannex A double integral integrates over two variables (so, effectively, over an area); a triple integral integrates over three (so, effective, a volume)
@gannex Imagine you're standing on the side of an axisymmetric hill. The gradient at that location points directly up to the peak of the hill.
Now imagine you walk 1/3 of the way around the hill.
The gradient at that location also points directly up to the peak of the hill.
Now, for a funky-shaped hill, at any given point the gradient might not point at the top of the hill. But, if you take a step in the direction of the gradient, you will always increase your altitude by the maximum amount possible for that starting point, even if that direction isn't pointed right at the top of the hill.
@gannex I also bookmarked it in Periodic Table for future reference: chat.stackexchange.com/rooms/3229/conversation/…
@orthocresol They're quite important for the theory and for implementing calculations. Most of the time when you're just running calculations, though, you don't have to worry about them very much.
@gannex I'd have to search out a reference, don't have one on hand, but going from LDA to GGA almost always gives improvements in just about every thing you might want to calculate.
It's less straightforward to improve on GGA -- it depends on what kind of system you have, and what you're trying to calculate.
Single hybrids, double hybrids, meta-functionals, fitted functionals, random-phase approximation, range-separated exchange... gets complex quickly. @Mart is a good one to ask about this.
Some ~related Chem.SE questions on DFT:
18
Q: DFT Functional Selection Criteria

AugI have a very very general question: In DFT functional selection , mostly people speak about the most recent ones. For example my professor always asks: " which DFT Functional did you select ? " and if I say B3LYP, he says : " No ! that's too old ! " but if I answer: M06 , he says : " hmm ... ...

computational-chemistry density-functional-theory
14
Q: DFT Code for Atoms : Sources

user23061Some time ago I implemented the restricted and unrestricted Hartree-Fock methods. I had a lot of fun and I learned a lot. It goes without saying that Szabo and Ostlund's book "Modern Quantum Chemistry" has been fundamental to achieve a working code. I would like to repeat the experience implemen...

quantum-chemistry computational-chemistry reference-request density-functional-theory
18
Q: Equivalent of Szabo and Ostlund book for DFT

user23061Szabo and Ostlund book Modern quantum chemistry [1] is extremely useful to understand Hartree-Fock and post-Hartree-Fock methods. Not only it explains the theory behind such methods, but it is also oriented towards a practical implementation. Following this book I was able to implement an Hartree...

software density-functional-theory books basis-set
9
Q: Are there any full worked examples of DFT calculations?

AugI just started learning DFT and now I am totally confused. Assuming I want to use B3LYP: \begin{align} v_s\left(\textbf{r}\right) &= v_\text{ext}\left(\textbf{r}\right) + \int d^3r\frac{n\left( \textbf{r}\right) }{\left|\textbf{r} - \textbf{r}^\prime\right|} + v_{\text{XC}}\left[ n \right]\left(...

computational-chemistry theoretical-chemistry quantum-chemistry density-functional-theory
 
M.A.R.
M.A.R.
7:50 PM
19
Q: 2016: a year in closing

Shog9A moderator asked me for data on the percentage of questions closed across all sites. This doesn't strike me as information that needs to be restricted to moderators, so for your idle enjoyment I present: Questions asked, closed and reopened for all sites in 2016 Site Name ...

discussion questions closed-questions statistics reopened-questions
Not about DFT, but definitely interesting numbers to watch
 
hBy2Py
hBy2Py
@hBy2Py I should clarify here -- in the hill analogy, altitude is $\Theta$ and is a two-dimensional variable of $x$ and $y$.
 
gannex
gannex
thanks @hBy2Py
I'm using the range-seperated hybrid functional wB97X-D. I did a bunch of calculations about a main group catalyst, and I'm just trying to write up a methods section to explain why GGA is so much better than LDA
 
hBy2Py
hBy2Py
Aha.
LDA only uses $\rho$
GGAs use $\nabla\rho$
 
gannex
gannex
I get the hill analogy
 
hBy2Py
hBy2Py
(in a complicated way)
 
gannex
gannex
7:52 PM
does this phrase make sense, then? : "The GGA includes a gradient of the density, which improves the accuracy of the approximation with respect to the local density approximation (LDA), which only employs the value of the density and tends to overestimate Exc."
 
hBy2Py
hBy2Py
Most meta-GGAs then further add in $\nabla^2\rho$, also in a complicated way.
Sure, that's a reasonable summary sentence
I'd change "includes a gradient of the density" to either "includes the gradient of the density" or "includes a function of the gradient of the density", though
 
gannex
gannex
hmmm. my PI said "employs the value of the density" was inaccurate somehow
 
hBy2Py
hBy2Py
Well, the functional uses the value of the density everywhere in the calculation
So it's not as though there's a single value of the density
 
gannex
gannex
yeah, I figured that was implicit.
 
hBy2Py
hBy2Py
It's the entire density function, $\rho\!\left(\vec r\right)$ that it depends on.
Not sure other than that why he would complain.
 
gannex
gannex
7:56 PM
hmm ok I think I'll just leave it.
the worst part is that all my files are corrupted now except the PDF, which I can't edit :-(
 
hBy2Py
hBy2Py
.docx?
 
gannex
gannex
yeah
 
hBy2Py
hBy2Py
Rename it to .docx.zip
 
gannex
gannex
Friday the 13th = bad luck computer day
 
hBy2Py
hBy2Py
.docx's are just zipped folders
 
gannex
gannex
7:57 PM
oh yeah?
 
hBy2Py
hBy2Py
somewhere in there is an xml file that probably has the majority of your text in there.
 
gannex
gannex
rename the corrupted .docx to .docx.zip?
OK
 
hBy2Py
hBy2Py
It will be a PITA to reconstruct, but easier than retyping it all
yep
simple rename
 
gannex
gannex
the thing is that I can get the text itself back, but reconstructing the references is going to take hours
I already recovered the text
 
hBy2Py
hBy2Py
Ahhh.
Yeah, that will suck. :-(
 
gannex
gannex
7:58 PM
yeah, there's no getting around it.
unless there's a way to convert the PDF to a word document
I just need to change a few sentences and rename the figures
 
hBy2Py
hBy2Py
There might be programs out there that'll do it, but I doubt there are any good ones that are free.
 
gannex
gannex
no, it'll be crap no matter what, but if I can save my references and text, then all I have to do is re-enter the figures and re-format everything.
anyways, I'm gonna get back to working on it. Thanks for the math tips!
 
hBy2Py
hBy2Py
Sure thing - good luck!
 
gannex
gannex
thx :P
hmmm... I found a freemium program that did it for me. It watermarked everything and ruined my figures, but I can copy the text into the orginal document and fix everything :D
 
hBy2Py
hBy2Py
8:34 PM
@gannex Woohoo! Thank goodness.
 
 
3 hours later…
Jan
Jan
11:17 PM
Dear mod team,
I’m terribly sorry for what I just did but I felt I had to do it. Thanks for not suspending me ;)
 
Loong
Loong
@Jan ?
 
Jan
Jan
I felt the need to add that. Dunno why.
 
Loong
Loong
aha
 
Loong
Loong
11:56 PM
@Jan "between manganate(VI) and manganate(VI)"?
 
Jan
Jan
@Loong I knew that was going to happen *sighs*
 

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