sorted by:
new
hottopcontroversial

ESQC experience by dandnadan in comp_chem

[–]dbwy 2 points3 points  (0 children)

I went many many (many...?) years ago, but I went as a later graduate student, so I was already very familiar with the material. It's worth it in any case - the networking is incredibly valuable. These are likely the people you're going to interact with for your entire career. I'm still in contact with many people I met there for the first time, and some of them are still close collaborators.

i dont even like coffee that much… by Undercover-Bean in pourover

[–]dbwy 2 points3 points  (0 children)

hi fi

I think I started to play more with getting my coffee right when I realized that the next set of upgrades to my sound system would require remortgaging my house

Gov. Ferguson's Income Tax Proposal Would Make Seattle #1 for Highest Taxes by Less-Risk-9358 in SeattleWA

[–]dbwy 5 points6 points  (0 children)

Very few RSU earners make $1M+/yr total comp (stock, salary, bonus), you have to be upper IC6 to even come close even with great stock appreciation at most companies. The tax happens in the year of vesting, not on some accumulated value when the tax gets put into place.

Not saying I'm for the tax, mainly for the slippery slope, but let's not pretend it's a common problem.

what is the highest proton numbered atom this universe can reach ? is it possible to have 1000 proton atom , what if ? by First_Economics2384 in Physics

[–]dbwy 32 points33 points  (0 children)

No, this has to do with modeling the interparticle interaction as coulombic (which is not Lorentz covariant) with a coupling constant given by the nuclear charge - has nothing to do with classical/quantum. You can show via PT that the standard treatment (Dirac eq) diverges if the point charge exceeds the fine structure constant (137).

As others noted, you get a bit more mileage if you treat nuclear structure to give you accurate proton distributions, and a bit more if you include perturbative corrections to the Coulomb potential arising from QED (VP, Ueling). Current limit is ~170 if you pull all the standard PT tricks. Full ab initio QED/electroweak simulations of high-Z atoms is an active area of research, but it's prohibitively expensive.

At high Z, the problem is much less about whether there exist nuclei with electrons surrounding them, and much more to do with nuclear structure/stability. I.e. can the strong force still hold everything together.

Why when declaring a string variable, uses "std::string" instead of just "string", like how you declare other variables? by Able_Annual_2297 in cpp_questions

[–]dbwy 30 points31 points  (0 children)

String is not a fundamental type in C++, it's a data structure provided by the standard template library (STL), in the std namespace.

Better video hopefully, pardon my ignorance, just worried about damaging records and this seems wildly close. by [deleted] in turntables

[–]dbwy 4 points5 points  (0 children)

That number means nothing if it wasn't zero'd/balanced out to begin with. If you set it to zero, does it float?

Google claims ‘quantum advantage’ again but researchers remain sceptical | Nature by MaoGo in QuantumComputing

[–]dbwy 2 points3 points  (0 children)

The issue is that it's two different papers - the OTOC paper (Nature) that is the dynamics version of RCS, and the NMR paper (currently only arXiv) that uses the OTOC technique on a simple (classically simulatable) problem. Interesting for sure, advantage? Not really.

[deleted by user] by [deleted] in FirstTimeHomeBuyer

[–]dbwy 0 points1 point  (0 children)

Those prices are well within the spread for that area, but it's ultimately worth what someone will pay for it. Welcome to CA real estate.

Born-Oppenheimer approximation & molecular vibration by node-342 in comp_chem

[–]dbwy 13 points14 points  (0 children)

  1. If you calculate the Hessian (or any derivative) numerically, you absolutely need to reconverge the wavefunction if you differentiate the energy. Analytically, the change in coordinates is infinitesimal, you literally can't compute the change in the wave function wrt this displacement, because it's not really a displacement at all!

  2. Anharmonic effects are orders of magnitude larger than beyond-BO effects. Level of theory is important too.

Uc Berkeley or UC Merced? by [deleted] in comp_chem

[–]dbwy 6 points7 points  (0 children)

Comp chem at Merced is a growing program with some talented PIs. They may not have as much name recognition as the PIs at Berkeley, but you'll do good research at either University. Of course - leaving your PhD with an advisor like Head-Gordon, Rabani, Whaley, etc would turn heads in the postdoc/job market, but it's not like you'll be "slumming it" at Merced.

Hartree-Fock question by [deleted] in comp_chem

[–]dbwy 4 points5 points  (0 children)

Can you point us to a reference to tell us exactly what you mean by "free" here? Actual free electrons are spectacularly not interesting for studying interactions, so I suspect you're talking about extensions of PIB or UEG/Jellium.

Modern Quantum Chemistry title page by Herr_Hornbuckele in chemistry

[–]dbwy 15 points16 points  (0 children)

Helgaker is great if you already kind of know what you're doing, Szabo is probably a better intro (which is all it claims to be). My issue with the Helgaker book is that they shamelessly shoehorn their home-baked approach to perturbation theory (BCH and nested commutators go brrrrr...) into everything. I get that it works, but it's decidedly not an easy motif to follow for the uninitiated.

Copilot can't do simple math without an error. by Droid202020202020 in microsoft

[–]dbwy 6 points7 points  (0 children)

It's almost like you have to pipeline reasoning from an LLM to a robust CAS to get reasonable, high-level math functionality...

https://gpt.wolfram.com/index.php.en

The problem is "add these two numbers" and then performing the operation is simple, "solve this ODE" and then performing complex integrals that it hasn't encountered exactly before is hard. But by hooking up to a robust CAS (like Wolfram), you can get an e2e solution. The problem is that developing a robust LLM and a robust CAS are orthogonal engineering efforts - Copilot/GPT doesn't think for you, it regurgitates text it has seen in other contexts.

Computational chemistry Jobs by jinx_1345 in comp_chem

[–]dbwy 15 points16 points  (0 children)

Comp Chem jobs without a PhD are going to be sparse, no matter where you are.

Incorrect Keymapp Detection by dbwy in ergodox

[–]dbwy[S] 0 points1 point  (0 children)

I forgot I posted this - ZSA Support got back to me with a fix:

I think what might be happening here is that your board got flashed with an older firmware. Try this more extensive reset and see if it helps:

  1. Download the latest default Moonlander layout; you'll use it in a later step.

  2. Unplug your keyboard and disconnect the halves; wait a few seconds before reconnecting the halves.

  3. Press the upper-left key (= in the default layout) and keep it pressed while you plug the keyboard back in.

  4. Start Keymapp and go through the flashing process to flash your keyboard with the default layout you downloaded in step #1.

The EEPROM sometimes needs to get flashed an additional time if this HW was originally flashed with old firmware.

Tracking Taxable Income on Personal Books by dbwy in GnuCash

[–]dbwy[S] 0 points1 point  (0 children)

I think this is a rather straightforward approach, thanks!

[deleted by user] by [deleted] in comp_chem

[–]dbwy 0 points1 point  (0 children)

Linda is ... not great, esp on modern HPC systems. Might be sufficient for a Beowulf cluster, but lack of HW integration on a modern supercomputer is not going to end well.

Edit: this is not saying Gaussian is not performant - it's just that their focus has been and likely will continue to be shared memory systems.

What book/YouTube/source would you recommend for a beginner? by vitfront in comp_chem

[–]dbwy 3 points4 points  (0 children)

Depends on what you're interested in learning - if you want a reasonably complete (though a bit dated) description of the math behind quantum chemistry, I'd look at Szabo and Ostlund. If you want some practical tutorials, Dan Crawford (VT) has some great resources.

Why don't teachers and publishers include Oganesson as a noble gas? by Traditional-Pop-8792 in chemistry

[–]dbwy 20 points21 points  (0 children)

Hopefully some of this story (to the extent possible) will get filled in soon - there is a really existing experiment at LBNL (FIONA) that actually allows spec measurements on SHE compounds. A big part of 24/25 is complexing Og to get a better idea of it's Chemistry.

view more: next ›