I just read this synopsis in Physics where scientists used first-principles nuclear physics calculations to predict the stability of 700 isotopes up to iron.

I didn't know that this was possible, especially for elements like iron, which would, as I understand it, a 3D strongly interacting quantum system with 50-60 particles.

The article says that ab initio methods are used for the nuclear physics, but are those related to the ab initio methods that we use in matter modeling? Or are they just using that term in the more general sense of meaning "from first principles"?

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    $\begingroup$ A key difference between quantum chemistry and nuclear physics is that in quantum chemistry we know the interaction exactly: it is the two-particle Coulomb operator. In contrast, nuclear physicists have to work with approximate forms of the interaction potentials, which can also have higher than two-body terms. $\endgroup$ – Susi Lehtola Jan 20 at 21:38
  • $\begingroup$ @SusiLehtola I've been trying to put together a book with all known many-body to 2-body transformations (a process which the quantum computing community calls "quadratization" because general Hamiltonians containing multi-qubit interactions must be "compiled" into quadratic Hamiltonians with at most 2-qubit interactions in order to run on the hardware which can only couple 2 qubits at a time). One of the applications of this is for running quantum chemistry calculations on quantum computing hardware, do you know of any references coming from the nuclear physics literature for approximating $\endgroup$ – Nike Dattani Jan 20 at 23:41
  • $\begingroup$ many-body terms in a Hamiltonian by 2-body terms, which could be added to my book arxiv.org/abs/1901.04405? $\endgroup$ – Nike Dattani Jan 20 at 23:42
  • $\begingroup$ @NikeDattani sorry, no... $\endgroup$ – Susi Lehtola Jan 20 at 23:52
  • $\begingroup$ It's worth noting, though, that the study referred to in the synopsis used two- and three-nucleon interactions, i.e. the Hamiltonian is much more complicated than the Coulombic one. $\endgroup$ – Susi Lehtola Jan 20 at 23:54

There is a long history of correlation between ab initio calculations for nuclear physics and ab initio calculations for quantum chemistry/materials.

Take coupled cluster for example, remembering that a lot of people used to say "CCSD(T) is the gold standard in quantum chemistry":

The method was initially developed by Fritz Coester and Hermann Kümmel in the 1950s for studying nuclear-physics phenomena, but became more frequently used when in 1966 Jiří Čížek (and later together with Josef Paldus) reformulated the method for electron correlation in atoms and molecules. It is now one of the most prevalent methods in quantum chemistry that includes electronic correlation.

The coupled cluster technique is a convenient model for many-particle wavefunctions, whether those systems are sub-atomic, atomic or super-atomic.

One of the most beautiful things about physics is that models like the Schroedinger equation are quite "universal" and therefore it can be used to model nuclei, atoms, molecules, macro-molecules, and so on, unless you need such high-precision as to need QED (quantum electrodynamics), QFD (quantum flavordynamics: if the weak force is needed), QCD (quantum colordynamics: if the strong force is needed, usually not for what your question is about but for sub-nuclear physics), or QGD (quantum gravity). But even if you did need QED, remember that QED is also universal in the same sense, and is in fact used for atomic and molecular calculations, as you can see in the references within this and this, and QED calculations would still be called ab initio in the same sense as Schroedinger equation solutions are, it's just that in quantum chemistry we don't always need to go beyond the Schroedinger equation.

Additionally I would like to mention that I wrote here that a lot of the foundational development of DFT was done by particle physicists (and the second link also includes references to seminal work by particle physicist Murray Gell-Mann):

My answers here and here also show that much of the early DFT development was done on the uniform electron gas, by particle physicists like Keith Brueckner and Jeffrey Goldstone (these two were also important players in the coupled cluster method, which is now developed and used much more by chemists).


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