@pentavalentcarbon hey man! so i have a quick question, you can answer whenever you have time. So remember you helped me out with comp chem stuff, and well since all of that was fun..I actually found somewhat of an opportunity to use it in my own research

So what I am interested in doing is computing rotational barriers for biphenyls substituted at the 2,2' and 6,6' and 4' position..these are pendants for a helical/helicogenic polymer and experimentally (interestingly) the 4' substituent has a an effect on helicity memory after helicity induction by a chiral small molecule

My guess is that the influence is electronic..(?) . Anyway, i think plotting rotation barriers vs the experimental data for helicity memory might be insightful

pubs.rsc.org/EN/content/articlehtml/2013/ob/c3ob26704k

pubs.rsc.org/en/content/articlepdf/2013/OB/C3OB26704K

pubs.acs.org/doi/abs/10.1021/jp0122124

^So far I have these papers as references

maybe eventually I would like to establish a link with electron withdrawing/electron donating ability of groups and helicity memory ala pubs.rsc.org/-/content/articlelanding/2016/cp/…

But anyway, more practical question is..what would you reckon is a good starting point for a method (guessing DFT) and a model chemistry?

I was thinking of using B3LYP-D, but i read ch.imperial.ac.uk/rzepa/blog/?p=1856 , and rzepa used WB97XD..which I guess might be better in this system since it will capture long range correlations better than B3LYP. That might be pertinent? Anyway, wanted to get your thoughts on it.

Let me know whenever you have some time.

Perhaps @Martin-マーチン might be able to chime in too? if you are free sometime?

@getafix I’ll read the papers my time tomorrow morning and get back to you. If you want to start messzing around, use a cheap functional (pure, no exchange like B97D or PBE with a correction) and a smallish basis (def2-SVP, pcseg-1).

@getafix I would advise against wB97DX, because it has never been reparametrised with Grimme's DFTD3 version, it still uses D2. For messing around I would, like @pentavalentcarbon suggested, also use something like BP86, PBE, M06L/M11L including empiricaldispersion=GD3BJ when available (otherwise 0-damping). Another option, where it is already included is B97D3. Use a split valence basis as suggested, with def-SVP you can even use density fitting. Which program are you using?

So I am in a synthetic group, but my supervisor has spoken to a theory group in the department and they will give me some time on their computers. They use gaussian I believe. To mess around, I will probably be using the copy of psi4 on mac

@Martin-マーチン so whats the difference between Grimme's DFTD3 and D2?

@getafix D3 is a redevelopment of D2 and it uses better parameters, more physics, less empiric

Oh alright I see.

Becke-Johnson damping gives the best results, but 0-damping is fine, too

I have no experience with psi4 though, but i guess those will be implemented.

for further discussion of theory stuff:

that's one thing I want to ask, what precise effect does damping have on the results? for instance, in my case..what do you suppose the difference would be in the rot. barriers with and without damping

Oh sweet! that's neat.

no idea what effect it actually has... BJ is physically more meaningful. It doesn't scale back disp to zero, but to a fixed value

I'd have to look for the papers again, because I don't remember all of it... the gist from Grimme's talk, however, was to use BJ whenever it is available

I'm so glad I implemented quota on my play computer... I played around with freqchk and it did write so much data, it would have crashed the system O.o

@getafix If you are using gaussian, you might find my tools helpful:

github.com/polyluxus/tools-for-g09.bash

@Martin-マーチン Thanks! I will take a look :). I will probably get started working on it in a week or so, still have some exams that need taking care of lol

@getafix good luck with that :D

I'm still working on those scripts, and they are not yet ported to g16, but I'm too busy taking care of that currently

just fixing the small problems one at the time...

^^ Honesty! I respect this.

When I start a sentence, is it "P-orbitals are ..." or "p-Orbitals are ..."?

@Martin-マーチン How, about the "The p-orbitals are..."? Not the answer to your question, but a workaround that just works :P

@GaurangTandon yes, in some cases that works, in others it might not be general enough; e.g.: "P-orbitals (or functions) are added to the basis set as polarisation functions." Adding a the at the front makes it too specific.

@Martin-マーチン I wonder if there's actually a rule for this capitalization in English grammar. This question hangs on the very boundary of chemistry and english language :O

Yes, indeed. I will for now avoid sentences like this...

@Martin-マーチン P-OrBitALs Are

@GaurangTandon there are no rules for capitalization. Just manuals of style

hmmm...

Mmmmmm

I would go with "p orbitals are"

Boils down to whether you care more about it being uncapitalized as a chem convention

Or capitalized as a capitalization convention

Don't betray chem

Chem needs your help. Yes, your help

ಠ_ಠ

My brain has now developed a reflex action towards sentences beginning with "p-orbitals are"...

@GaurangTandon tsk tsk tsk Mart must be illiterate

@M.A.R. No i didn't mean that :(

Obviously it should be sorbitles, porbitles, dorbitles, forbitles, gorbitles, horbitles, ...

@Martin-マーチン sorbitol is some kinda drug

Oh

that's why sorbitles

no confusion possible

y u no trust the wikipedia?

@Martin-マーチン no confusion possible either if we just call them Bob, Pam, John, etc.

Martin, Ronald

We'd call P-OrBitALs Martin because you look like a cylinder

@M.A.R. I like that! Pam is added as a polarisation function. would make a lot of quantum chemistry texts more entertaining...

Wait, maybe your hat does

Anyway you remind me of cylinders

which kind?

carp...

@Martin-マーチン see, definition 5 says H.G.Wells is a cylinder

You probably look like H.G.Wells

I have way less hair... that's why the hat...

Man, he might even be your grandpa

Martin C. ShwarWells

@Martin-マーチン being bald is sexy to most. You should just put off the hat

@M.A.R. too cold!

@Martin-マーチン come on, you're not living in the south pole

@M.A.R. That's true, but I am sensitive...

@Martin-マーチン I use p-Orbitals.

To me it's analogous to "meta-Nitrobenzoic acid was synthesised..."

cool tanks!

> detox my armpits

:D

@pentavalentcarbon You mean you don't? Eww. Gross.

If you don't detox your armpits, do I even want to do this mock interview with you???

@orthocresol Well, I do, but only using organic chemicals, nothing synthetic, never mind anything inorganic.

@Zhe 1. We're ~560 miles apart. 2. I'm getting a haircut that morning, does that count?

I should get back to that...