Electronic Structure of LK-99 (opens in new tab)

To be honest, this is a hunch thing more than a I can teach and explain it thing. To me it's just "a lot of the same stories" that are told about cuprates, and less of a "I can explain the mechanism".

Roughly, one of the "properties" that shows up with these materials is that the 3d orbitals of coper atoms are involved in forming the bands near the fermi level. Couple that with the fun story of Cu electron configuration being [Ar] 3d^10 4s^1, which suggests that spin-effects are "at play" with these electrons near their filling levels. Combine that with the spin-character properties of cuprate paring (eg. s-wave vs. d-wave superconductors, (d-wave for BSCCO for instance)). All together it lends itself to a nice spin-orbit coupled band "setup" at the fermi energy that I have a hunch somehow backs the underlying mechanism of these d-wave superconductors. Fully admit, there's some leaps there in the raw logic -- if I could fully explain it I probably would still be in the field, haha.

I'll note: I've been out of the field for ~8 years, but a quick google search led to some more recent papers [1][2] working through plausible explanations based on some of these copper d orbital shenanigans.

[1] https://www.scirp.org/journal/paperinformation.aspx?paperid=... [2] https://arxiv.org/abs/2105.11664 (d-p, but includes the Cu d-orbital and also specifically states "We also show that the effect of the nearest-neighbor d-d Coulomb interaction Vdd is actually quite important for the stability of superconductivity and phase competition.")

Because materials interfaces create weird effects.

You would use metals as your leads and create Josephson-junctions-like interfaces.

Basically the abrupt change in electron mobility across materials can cause knock on effects that dominate what you are trying to measure.

Interfacial engineering is one term in materials science that implements best practices for dealing with such challenges.

Measuring zero resistance turns out to be quite difficult because your measuring apparatus tends to have some resistance in itself.

Perhaps heating it up while it levitates would be a better idea. Put the magnet in an oven together with the sample and bake?

Well, I guess, that are islands of superconductivity and normal conductivity in the same sample.

This gives a low resistance and diamagnetism which is used as proxy to real superconductivity.

I may be wrong though.

I think if it was actually zero it would be? The issue I think is impurity/defects in the manufactured samples, so there's non-superconducting bits in addition to the allegedly superconducting bits.

Just guessing: I would say not enough because the sample is extremely small and there is chance that the electrons jump from each sides of the probes, skipping the sample ? (like a short-circuit) + the fact that the probes themselves are not superconductor, so there is a natural accepted tolerance in the measures (claimed to be due to the probes)

It looks like the citation of the Pais patent was added by the examiner, rather than by the applicants. Does that make any difference in your view?

If something is prior art, you need to include it, regardless of the source. Even fictional descriptions of technologies can be prior art. For example, Samsung used 2001 A Space Odyssey as prior art to invalidate Apple's patent on ipad-like tablets.

I wouldn't read too much into this. You have to address prior art when it is found in patent examination as a part of application process, no matter how bogus it is.

Cited patents are added by the examiner. Source: I have several patents.

Would be pretty funny if this guy actually published a breakthrough that worked all of a sudden

I wonder why more people aren't talking about this

I thought the inclusion of Pais' patents was more along the lines of, here is a patent related to our work, rather than we sourced tech from it.

I'd probably approach 90% confidence with ~2-3 different measurements from different labs showing similar stories. Select from the grab bag of possible experiments that could all collaborate and provide consistency in their stories: specifically things like measuring the critical current, critical magnetic field, high quality electrical resistance in various ways (lots of transport), STM measurements of gaps, ARPES measurements of gaps, XRD showing crystal structures are what we expect that matches the DFT, a study on the domain sizes/effects (since this is relying on a substition at the right place, necessarily I suspect that there will be domain effects / "doping" style things... so how those play out in terms of purity and quality of results will be interesting). There will be a lot to study and characterize, and every extra measurement that is consistent rapidly increases that confidence. I'd say I'd get to "100%" (as close as someone could be) after ~10-20 papers across many different labs and measurements. I'd hope we'd get there in ~3-6 months.

What I'm actually even slightly more excited about is "what comes next" -- not the market part, but the "fast follow science". For instance, in the few years after LCBO and LSCO were found (TC~30K) we quickly found YBCO and BSCCO (Tc~130K). I would expect that we'll find a whole class of these materials with substitution tricks that possibly work, and there will be a whole slew of options for "going to market" with the technology. The door this opens is what is more exciting than the specifics of LK-99 itself in my opinion.

Estimating times, after the fast follow science (0.5-2 years optimistically?) we will hopefully have the actual "we're all convinced this is real, and the technology can start to be applied in real devices". Specifically, after everyone is pretty clear on a lot of the material properties and ways to reproducibly make high-quality crystals, so consistency is clear on measurements... then begins the cycles on how to manufacture high enough quality material at scale that it can actually be applied. (specifically, these materials (assuming they're like YCBO/BSCCO) are superconducting crystals that have grains, alignment issues, are physically brittle, have homogeneity issues, etc.) While each solvable, these are all real engineering and material challenges that increase cost to manufacture, and all of this will probably take time before we suddenly get wide-scale products that use this (this is all assuming it's real, haha, there's still plenty of reason to be skeptical).

I'm not a scientist, but personally I expect I'll have two "wow, this is really happening" moments:

(1) When there's peer-reviewed replication from a group of reputable labs.

(2) When I see the classic superconductor-on-magnetic-track demo, but without liquid nitrogen.

Waiting for Applied Science (the YouTuber) to make some in his lab.

If you haven't seen it, levitating frogs are also quite wonderful. https://slate.com/business/2014/05/nobel-prize-in-physics-an...

An Ig Nobel AND a Nobel. That's quite the achievement.

Any conductive material for the tube will have a similar effect. It isn't specific to copper.

The moving magnet induces a current in the tube which in turn creates the magnetic field that interacts with the magnet.

A diamagnetic material.

"In simple terms, diamagnetic materials are substances that are usually repelled by a magnetic field. Electrons in an atom revolve around the nucleus, and thus possess orbital angular momentum. The resultant magnetic momentum in an atom of the diamagnetic material is zero."

The Meissner effect requires a temperature transition in the diamagnetic behaviour. As you increase the temperature, you would expect a sharp drop with the material falling back on the magnet, and then levitating again once the temperature drops.

Impact of superconductors: https://threadreaderapp.com/thread/1685088625187495936.html

"zero ohms" is very tricky to measure because of contact resistance: your probes aren't superconducting, and the thin contact surface between your probes and the metal itself isn't superconducting either.

Whereas the Meissner effect is unique to superconductors. It just has to be distinguished from diamagnetism, and there are materials which are strongly diamagnetic but not superconductors.

Because the levitation thing works with tiny fragments too whereas the 'zero Ohms' measurement only works when you have enough of it to form a long enough wire of it that you could tell the difference between 0 and 0.000001. Measuring very small resistances is usually done by letting a known current run through them and then to measure the voltage across the sample using known resistance leads. For a superconductor that has a tiny available sample which is already conductive even if it is not superconducting is fraught with error and may well give you the wrong answer due to a tiny measuring error.

But the Meissner effect is a unique signature of a diamagnetic material and will provide you some evidence even if the sample is tiny. So I understand why they have not yet resorted to other measurements, if there is no Meissner effect you don't need to continue with the hard work of trying to make a wire (which may well be a serious challenge for this stuff, the yield will have to come up significantly before that's a real possibility).

hth

Build a loop out of a superconductor, induce a current in it, and then measure the resulting magnetic field after a couple of minutes.

If the field is still there, then you have a superconductor.

I’ve published in computational solid state. My doctorate is, on paper, in earth sciences (mineral sciences!) and you’re going to find all of the materials science department and a few engineers in the vicinity too. Solid-state is one of those five-way borders in the Benelux countries where everyone speaks three languages.

When a material shrinks, it can create immense internal stresses equivalent to what it would experience at extreme pressures. Compare to say a Prince Rupert's drop.

Indeed. The separation between "Chemistry" and "Physics" completely breaks down when you start dealing with electron behaviours.

I've actually got a little tin-foil-hat pet theory that Chemistry is slowly dying as it approaches "completion" of its roots (macroscopic phenomena of matter), and is gradually being subsumed by Physics. To at least a silly layman like me, lots of bleeding-edge Chemistry nowadays reads like your average Physics, e.g. doing quantum simulations for protein folding, superconductors, etc.

I'm probably just being silly though, right?

Kwon is humanities' hero for leaking this knowledge to the world

Im sure I’m not the only person thinking 24 years is way too long for such an important advancement.

Huge respect for those in this field or others that don’t give up after so many years. Thank you

So... He leaked and claimed it was because he feared someone else would do it before him?

> but also why the samples seem to teeter on the edge of superconductivity so frustratingly.

Interesting! The uneven chunk shown in the original video was probably the best specimen they had after decades of attempts.

When I first saw it, my first thought was, "geez, why not at least try to make it uniform"...

I have the same thought: "25 years? Why the fuck. Buy a new salt and publish a fucking paper."

I suppose they saw something favorable in that 99 sample and nobody else knew. The vagaries of chemical synthesis helped.

But it doesn't seem like they could have had a worse sample than what they fucking have now, while getting data that made them waste a quarter-century.

As much as people hype and have 'reproduced' it, I...dunno. If it's real, the autobiography will be worth an expensive translation.

Speaks to a supreme confidence in the theory, surely? I'm a layman but imagine everyone is going to want to hear every wild idea these guys could think up if this works out. They might have been sitting on this for 20 years? Probably why I'm not, but If I were any vc person I'd be busting down their door trying to give them all my money

For anyone else totally clueless about chemistry: According to Wikipedia DFT in this context stands for 'Density-functional theory' and not 'Discrete Fourier Transform' as I assumed given the references to waves.

How about Quantum Espresso [1] and CP2K [2]? They're both open source

[1] https://www.quantum-espresso.org/ [2] https://www.cp2k.org/

Not sure if you're implying she's cooked up a few crucibles at home purely for internet attention (nor what the relevance of her political views are here), but regardless the thread is interesting either way as it's generating lot of general interest in replication. This is perhaps a better link: https://eirifu.wordpress.com/2023/07/30/lk-99-superconductor...

Thank you! Edited & will try use in future.

Thank you for the reply. This is helpful.

Thanks for linking someone who knows what he's talking about, very painful to see these DFT papers overhyped as some kind of proof... It proves almost nothing

Yeah the techbros have been the worst. Coffee guy went from saying the first DFT paper should deserve a Nobel to, "it's not a strong signal of anything" in 12 hours. WTF. All the actual scientists have been rock steady at, "it is probably not going to replicate," especially CMTC.

Techbro speculation on physics should be considered harmful.

It's basically an open secret, no one really believes DFT has much predictive power in strongly correlated systems (where relevant electrons cannot be treated as independent). It's not useless, but DFT calculations require many arbitrary choices and are hardly "first principles" in a meaningful way.

DFT is generally good for well characterized phenomenon. Superconductivity is a bit of an edge case, really dependent on quantum effects that you need ab-initio quantum mechanics simulations to predict.

There’s an old saying that “simulations are bound to succeed,” but also as an academic that has a working knowledge of statistical mechanics but is not a (condensed matter) physicist, from what I’ve read it seems folks are approaching this with healthy skepticism likely due to the drama around the development and release of the first paper.

The simulation paper folks are talking about used what appeared to be an existing DFT simulation package. Now, DFT is an approximate theory used to render computation tractable, but to my understanding it is a popular and mature method. I was actually kind of impressed that they were able to reproduce results from the LK paper in simulation so quickly. While it’s possible the speed led to a bug or error in the analysis, simulations often don’t just magically work and can take a decent amount of parameter tuning — especially if the system being simulated has something tricky or exotic going on. The fact that they were able to get what appears to be an accurate simulation working quickly that also justifies the low yield rates has made me more cautiously optimistic than anything

I don't know why anyone should be concerned about anything here, unless you want immediate confirmation.

It's a process. Scientists will try to replicate and try to simulate and try to reason theoretically. They are bound to make mistakes but all of this can be critiqued and iterated on.

Again, there's no problem unless you need immediate confirmation or you think chasing this idea is a waste of time.

Enjoy the ride :)

This could also explain why the original authors themselves say they can only make it successfully around 1/10 times. The stars need to align.

Berkeley's Sinead Griffin.

"Origin of correlated isolated flat bands in copper-substituted lead phosphate apatite" (2023) https://arxiv.org/abs/2307.16892 :

> Abstract: A recent report of room temperature superconductivity at ambient pressure in Cu-substituted apatite (`LK99') has invigorated interest in the understanding of what materials and mechanisms can allow for high-temperature superconductivity. Here I perform density functional theory calculations on Cu-substituted lead phosphate apatite, identifying correlated isolated flat bands at the Fermi level, a common signature of high transition temperatures in already established families of superconductors. I elucidate the origins of these isolated bands as arising from a structural distortion induced by the Cu ions and a chiral charge density wave from the Pb lone pairs. These results suggest that a minimal two-band model can encompass much of the low-energy physics in this system. Finally, I discuss the implications of my results on possible superconductivity in Cu-doped apatite

I think she's working in a UC Berkeley Lab

Sure it’s post hoc, but these are ab initio calculations, there’s not all that much wiggle room that you could make anything you like come out looking like a superconductor. Plus now I’ve seen three calculations with three different functionals and reasonable convergence criteria and they all find similar electronic structure

Unidentified Flying Objects are absolutely real, though the newer cool kid term is UAP.

(From the internet: UAP stands for "unidentified anomalous phenomena.")

It's flying saucers carrying aliens from another planet that's controversial and up for debate.

USAF has had LK-99 for 20 years and the UFOs are just sightings of them testing levitation engines.

> Over four months, March through June 1905, Albert Einstein produced four papers that revolutionized science. One explained how to measure the size of molecules in a liquid, a second posited how to determine their movement, and a third described how light comes in packets called photons—the foundation of quantum physics and the idea that eventually won him the Nobel Prize. A fourth paper introduced special relativity, leading physicists to reconsider notions of space and time that had sufficed since the dawn of civilization. Then, a few months later, almost as an afterthought, Einstein pointed out in a fifth paper that matter and energy can be interchangeable at the atomic level specifically, that E=mc2, the scientific basis of nuclear energy and the most famous mathematical equation in history.

https://www.smithsonianmag.com/science-nature/the-year-of-al...

The year we realized that Crypto was all a fraud

I felt like it lasted much longer. Of course, this was pre Internet days, so I read it in papers and watched on TV

Perhaps poorly worded, I meant since before. During Covid I lost a lot of zest for life, felt like I went to sleep in my 20s and woke up an old man.

Once in a lifetime events tend to be "Exciting" to people, watching history unfold so to speak. The excitement comes from the awareness of this fact, and the fact that it might never be seen again.

When lockdown first happened it was exciting. Nothing like that has happened in most people's lifetimes.

Of course it for tedious very quickly, but I remember going to the park and people being told not to sit on benches by police on horseback. How is that not crazy and sort of exciting?

Emotionally, it was horrible. Societally, it was depressing to see that we'll never be able to tackle any true large problems, we can't even agree on wearing a piece of paper to protect fellow humans.

But scientifically? Yeah, I'll go with "exciting". The field seemed to move at a tremendous speed, or at least that's how it looked to me as an outsider.

Sequencing within less than a week, extremely rapid movement on the mRNA front (and really, the whole vaccination field - 200 candidates in 9 months), revamped understanding of aerosol transmission, leaps in rapid modelling, tremendous progress in terms of test development, growth in international collaboration, progress in the (public) understanding of chronic diseases, scaling up of wastewater monitoring, ...

Definitely exciting.

mRNA vaccines are a huge discovery, not quite as powerful as room temperature superconductors but still up there in terms of impact on humanity. And encountered a very different kind of skepticism while ultimately turning out to be not only real but widely deployed with great speed.

He didn't say "since COVID" but "since before COVID." COVID isn't the exciting event, it's an arbitrary landmark.

I think it's the videos of levitating samples that people are getting excited about. At this point it's either outright fraud (unlikely), an interesting materials science discovery that isn't superconductivity (most likely IMO), or superconductivity itself (still unlikely, but the balance of evidence is shifting).

If it happens to be the latter, it's a huge scientific leap forward.

What makes this hype "manufactured"? I've been very hyped as well ever since I read the arxiv.

Most people are powerless to do anything so they associate themselves with movements to feel as if they are part of something meaningful

On the contrary.

Should he rather be excited about hype manufactured by entertainment or sport companies? Cause that's much more common.

I think we're all horribly burned out by pop-science. How many battery "breakthroughs" have we seen on here? Meanwhile what actually works is incremental improvement in lithium battery manufacturing.

The 1947 Golden Age SF is interesting because the "rocket fanatics" peaked in 1969 and humans haven't gone back to the moon, let alone conquered space. While the transistor succeeded to an extent nobody imagined due to the magic of compounding improvements.

> You see a stupid silly black fleck floating over a magnet

Meanwhile over in the AI "optimism" channel people are telling us that AI will be able to produce videos of anything that are indistinguishable from reality, and that we should all learn never to believe video evidence again.

I'm still very much in the "don't know" camp on the superconductor, but what I do know is that it's not worth getting excited until we know it's real.

I think it's equally wrong to compare this whole thing to solar panels and whatnot.

That said, in general, 9 out of 10 things that are very promising will ultimately fail, and there's nothing wrong with discussing or following all 10, the 1 will work, and it'll be great.

That's funny too, but I think you can do both. You can be interested, but also make fun of it. I have a suspicion, that in the long term, being able to keep it light and make fun of the serious work that you do actually assists your longevity, resilience, creativity and productivity in working on it.

It may not be true, but some amount of keeping it light definitely works for me. I mean I love taking myself seriously too. And some amount of doing that I think is necessary. I guess I just don't wanna put all my eggs in one strategic-approach basket, you know? People are complex! :)

>Similar trends can be observed rectro-actively for practical solar panels, micro electronics, powered flight and so on. All had their skeptics

Isn't this textbook survivorship bias?

On the grand scale, I bet the skeptics have a much better record than the optimists.

Despite the the "strictly no jesting on the super serious hacker news" rule, I think it was just a joke. I wouldn't let it get to you too much. I thought it was pretty funny.

Same with me, it gives me the same feeling of "Living in a science fiction world" that I once felt when cell phones or Google maps came out.

Of course even tough I still use both profusely every day, the feeling of novelty wore out. I expect the same will happen with this.

I would say I am in both worlds. Not too excited about a lot developments in computer tech, but mostly because there is a lot of hype on technology that tends be impressive BUT misses the mark on the bold claims.

But with this LK99 stuff, there is not much room for vague wiggle room. The requirements are very clearly defined and if they do it. It is done! It isn't a case of "if in 5 years and $X billion we may be able to produce this stuff", it is a case of they showing a working material.

It is hard not to be excited for this!

And there’s the third group that likes to comment on meta-hn behavior in a disparaging way

Sometimes it's so difficult to continue to feel positive about science news when there have been so many instances of false hope. Cautiously optimistic is the best position to be in, I think.

That being said:

I want the magical floating rocks to be real.

I want the talky computer to be self aware and capable of genuine creation.

I want the explanation for UAPs to be aliens.

I want reactionless engine technology.

I definitely still feel excited by things, but time has taught me to temper it.

It seems to me that the second group is also entertained by discussing money, tech salaries in particular.

From my perspective, LK-99 is by far the most likely to be an actual serious technological breakthrough. If it's real, it would be a breakthrough on the level of the discovery of electricity, the lens, the transistor, or the laser. One of those era-defining bottlenecks in the Civilization technology tree.

GPT-4 is a nice iterative improvement over previous work, and a culmination of decades of research. It's not anywhere near an AGI and it's close to the limit of what we can accomplish with our current understanding of AI and our current availability of good data. We're near the top of the sigmoid curve on this one; new advances are going to come from specializing and integrating these models, not just making bigger ones.

The fusion "breakthrough" is seriously underwhelming when you look at the total power in/out of the whole plant, not just a tiny tunnel-visioned window of the fusion reaction itself (ignoring power of magnetic confinement and the laser pulse), and even more when you think about how much tritium humanity has ever created. We're just not seeing what we need here and the net power output is still deeply in the negative.

Lol aliens.

My point, to both you and GP, is that it's quite possible to have very different levels of optimism for these recent revelations, and it's not hypocritical to do so. Details and context matter. Dozens of materials science Ph.D.s saying "holy shit this looks like the real deal guys" vs. one guy saying "someone told me there were hidden stocks of blinker fluid that I wasn't allowed to see" just does not engender the same confidence levels.

> 3. In May we find out apparently our government has recovered alien technologies

This is a silly thing to include on the list since it doesn't seem to be true?

Regarding #1, it pains me to see so much hype about this feat.

To restate it. We were able to simulate the implosion of the secondary stage of a thermonuclear device in a lab by the means of lasers, to the point that this simulation has ~ 0.001% the efficiency of a real device.

We also probably learned a lot about the amplification of x-rays by the casing material that would have been useful during the SDI days of the early 80s.

tldr; It was a weapons test, by a weapons lab.

But at the same time, we may already be in the early stages of the collapse of western civilisation, with or without Russia/Ukraine escalating into WW3.

Having played through Portal 2 again recently, it's like the equivalent of GlaDOS scheming to take back over the Aperture Science Facility while she's only getting 1.1 Volts from the potato.

The oneshot or short session manner in which AI are typically used does not have a rogue potential.

The AI would need to have a virtually unreachable goal, and run in an endless loop, to be able to drift its goals to be at odds with humanity.

people forget that AI was already in control of the markets since 2014 at least. it's bootstrapping

Perhaps, but the reverse engineering efforts you mention may have already led to incredible breakthroughs over the past few decades. Lasers, integrated circuits, Kevlar, fiber optics, and more technologies were said to have been seeded among the research community based on recovered UAP components. This is based on Army Colonel Philip Corso’s account in his memoir, “The Day After Roswell”. [1]

[1] https://en.wikipedia.org/wiki/The_Day_After_Roswell

I’ve seen several tweets implying the gubberment is rushing out RTAPS to “cover up” the alien stuff

The object in the IR Tic-Tac video is colder than the environment. High current supraconductivity will perhaps always require a low temperature.

You think all of the news about crypto fraud might have a chilling effect on the excitation?

If thanks to those technologies new hyper-efficient compute and network hardware becomes the norm, and there is no meaningful difference between decentralized hosting and centralized hosting of services/apps/games, crypto will likely see renewed interest.

People are still unhappy with the decisions of single IP owners controlling the platforms and games they use on a daily basis. Decentralized ledger technology, whether blockchain or not, offers an alternative.

Web 3.0 was so exciting with btc at 64k

> I despise generative LLMs and avoid using them at every opportunity.

why? it's just a tool.

despise how it was released, how it was trained, the people that operate it , whatever, but I can't really understand why someone would 'despise' a wrench -- even if it was used really poorly and produced by a shady company with a checkered past.

Seems a bit foolish to leave that space on your toolbelt empty.

The next breakthrough we need is with fusion technology. With unlimited fusion energy, room temperature superconductivity, and (soon) artificial general intelligence, the singularity won't be long off.

not with that attitude it isn’t

Bitcoin was really 'done' 10 years ago. It does what it does and there really isn't much more to it. People tried to keep the hype going with DAO's, earn programs, smart contracts, NFT's, etc.. but crypto was already done before 'web3' even started.

Like Theranos, the secret ingredient turned out to be fraud, and the big threat is jail.

Hey, who knows, it could just be a scaling issue. (The history of NNs would lend credence to this theory). In which case, if this room temperature superconductor stuff is legit, then maybe we're about to experience a major compute power leap that could result in AGI sooner than we think.

What makes you think we're lacking fundamental plumbing? I am personally still quite convinced it will simply take a bit of time and development to plug in the current AI into sufficient self-testing structures (basically the next versions of AutoGPT) and let it run long enough to map out an entire domain with accurate measurements. Seems more like just a matter of time and a bit of funding - but mostly inevitable and very straightforward. It doesn't even really take GPT4 quality levels to do - that's just a bonus.

https://twitter.com/fablesimulation/status/16813529041528504... These guys seem to be on the leading edge there - making self-referential character-driven narratives where agents talk to each other and build the collective world understanding, all through a South Park Westworld lol

It's not dumber. You can verify this on their models with any prompt you ran at 0.0 when it first came out, I did. It's the exact same model run the same exact way. They've repeatedly confirmed this.

> lead free solder has been much more damaging for the environment because of all the e-waste it created.

We're getting quite off-topic here (I guess I should have used different examples), but I would be interested where you got that information from. Most consumer electronics devices do not break prematurely, and especially not due to soldering issues. Source: I buy most electronics second-hand, I regularly repair electronics RoHS and not RoHS, I use lead-free solder and occasionally leaded solder, I watch a bunch of Youtube videos by other people who repair a bunch of electronics, just for fun. (You'll always (and easily) find someone who knows more than me, and it's entirely possible that you do.)

Most consumer electronics devices are retired because their owners got something shinier, or if "broken", it's the battery, display, or some important connector. If something is "actually" broken, it's usually due to power ICs, capacitors, fuses. (You could of course argue that some broken connectors are a case of a soldering issue, but yeah, it's not like I haven't seen broken connectors that were actually soldered using leaded solder, so things can get kind of muddy there)