arxiv: 2604.25418 · v1 · submitted 2026-04-28 · ⚛️ nucl-th

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Large-scale fission data generation with BSkG3

Adri\'an S\'anchez-Fern\'andez , Wouter Ryssens , St\'ephane Goriely

Authors on Pith no claims yet

Pith reviewed 2026-05-07 14:19 UTC · model grok-4.3

classification ⚛️ nucl-th

keywords fission barriersspontaneous fission half-livesenergy density functionalBSkG3r-process nucleosynthesisheavy nucleiMOCCaleast-action principle

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The pith

Fission barriers and spontaneous fission half-lives are computed for roughly 3300 heavy nuclei with the BSkG3 functional.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper generates a large dataset of fission properties across the heaviest nuclei by combining an existing energy density functional with an efficient structure code. It includes triaxial and octupole deformations, covers even-even, odd, and odd-odd systems, and selects fission paths according to the least-action principle. The resulting primary barriers and half-lives are presented directly. These quantities are then examined for their consequences in models of heavy-element formation. A reader would care because fission rates control how far the r-process can proceed before nuclei split.

Core claim

Using the efficiency of the MOCCa nuclear structure code and the predictive power of the BSkG3 energy density functional, we systematically study fission properties of the heaviest nuclei (roughly 3,300) accounting for (1) axial, triaxial and octupole moment; (2) all nuclei, including odd and odd-odd systems; and (3) fission paths determined via the least-action principle. We present the set of primary fission barriers and spontaneous fission half-lives we obtain and discuss their implications for r-process nucleosynthesis.

What carries the argument

The BSkG3 energy density functional run inside the MOCCa code to locate least-action fission paths in a space of axial, triaxial, and octupole collective coordinates.

If this is right

A ready-to-use table of primary fission barriers exists for all nuclei up to the heaviest stable and near-stable species.
Spontaneous fission half-lives become available for odd and odd-odd nuclei that are usually omitted.
The new rates can be inserted directly into r-process network calculations to test whether fission cycling alters final abundance patterns.
Systematic trends in barrier heights across the chart of nuclides become visible without manual case-by-case tuning.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The same computational setup could be rerun with other energy density functionals to produce a direct comparison set of fission data.
The inclusion of odd nuclei removes a common source of uncertainty when estimating fission rates in astrophysical environments.
If the barriers prove consistent with future measurements near the r-process path, the dataset could serve as a benchmark for simpler phenomenological models.

Load-bearing premise

The BSkG3 functional, already fitted to other nuclear data, still gives reliable fission barriers and half-lives when only axial, triaxial, and octupole shapes are considered.

What would settle it

A clear mismatch between the computed spontaneous fission half-lives and measured values for several well-studied heavy nuclei would show the calculations are not accurate enough.

Figures

Figures reproduced from arXiv: 2604.25418 by Adri\'an S\'anchez-Fern\'andez, St\'ephane Goriely, Wouter Ryssens.

**Figure 1.** Figure 1: Upper panel: 240Pu PES with the LAP (black dots) and the saddles/wells (yellow stars/grey squares). Middle panel: Energy (black line) and microscopic collective inertia (red line) along the LAP; Blue lines denote the empirical values from RIPL-3 [15]. Lower panel: evolution of the axial octupole deformation along the LAP. This level of agreement for barriers is superior to that achieved by other microscopi… view at source ↗

read the original abstract

Modeling fission properties, such as barriers and rates, is highly challenging. The most microscopic methods available are based on energy density functionals (EDFs) and rely on a limited set of collective coordinates to describe the evolution of a fissioning nucleus from its ground state to scission. Leveraging the efficiency of the MOCCa nuclear structure code and the predictive power of the BSkG3 EDF, we systematically study fission properties of the heaviest nuclei (roughly 3,300) accounting for (1) axial, triaxial and octupole moment; (2) all nuclei, including odd and odd-odd systems; and (3) fission paths determined via the least-action principle. We present the set of primary fission barriers and spontaneous fission half-lives we obtain and discuss their implications for r-process nucleosynthesis.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This paper generates a new large dataset of fission barriers and half-lives for 3300 nuclei with BSkG3, extending prior work to odd nuclei and non-axial shapes, but its usefulness rests on unverified accuracy for fission paths.

read the letter

The punchline is that this work produces a new tabulated set of primary fission barriers and spontaneous fission half-lives for around 3300 nuclei, including odd and odd-odd systems with triaxial and octupole effects via least-action paths. This extends prior BSkG calculations in scale and scope. What the paper does well is apply the established BSkG3 functional and MOCCa code efficiently to generate this volume of data without introducing new parameters or fits. The inclusion of non-axial shapes and odd nuclei fills gaps in previous large-scale efforts, and the least-action principle for paths is a reasonable choice for determining the dominant fission route. The soft spots are around validation and transferability. The BSkG3 EDF was tuned to ground-state masses and such, but fission involves extreme deformations where the functional's behavior is less constrained. For odd nuclei, the treatment of blocking can introduce additional uncertainties. The abstract discusses r-process implications, but if the full paper lacks extensive comparisons to experimental barriers or half-lives, or sensitivity studies, then the dataset's usefulness for nucleosynthesis could be limited by systematic offsets of a few MeV in barriers, which exponentially affect rates. The stress-test concern about extrapolation holds unless the paper shows otherwise. This paper is aimed at researchers in nuclear astrophysics who model the r-process and need comprehensive fission data for heavy nuclei. A reader focused on abundance predictions would find the tables directly applicable, assuming the numbers are accurate enough. It deserves serious peer review because the computational scale is substantial and the dataset is novel, allowing referees to evaluate the technical implementation and any supporting checks.

Referee Report

2 major / 2 minor

Summary. The manuscript presents a systematic large-scale computation of primary fission barriers and spontaneous fission half-lives for roughly 3300 heavy nuclei using the BSkG3 energy density functional within the MOCCa code. It incorporates axial, triaxial, and octupole collective coordinates, treats even-even, odd, and odd-odd systems, determines fission paths via the least-action principle, and discusses the implications of the resulting dataset for r-process nucleosynthesis.

Significance. If the central results hold, the work would deliver a valuable, systematically generated dataset for fission properties in the heaviest nuclei, where experimental data are sparse. The inclusion of triaxial/octupole shapes, odd nuclei, and least-action paths represents a methodological advance over many prior surveys. The potential utility for r-process modeling is clear, provided the BSkG3 functional retains quantitative accuracy along the fission valleys at large deformations and extreme neutron excess.

major comments (2)

[Results and validation discussion] The central claim that BSkG3 yields usable barriers and half-lives for ~3300 nuclei (including odd/odd-odd systems) rests on the unverified transferability of an EDF previously fitted to ground-state masses and selected deformations. The manuscript does not report a dedicated validation subsection comparing calculated primary barriers against the available experimental fission-barrier data for known heavy nuclei, particularly odd-mass cases; without such benchmarks and quantified discrepancies, the reliability of the extrapolated dataset cannot be assessed.
[Methods and collective-coordinate section] The least-action principle is invoked to select fission paths, yet the paper provides no explicit test of how the inclusion of triaxial and octupole coordinates alters the action integrals or barriers relative to purely axial calculations for a representative subset of nuclei. This omission is load-bearing because the abstract highlights these coordinates as a key improvement, but their quantitative impact on the final barriers and half-lives is not demonstrated.

minor comments (2)

[Methods] Notation for the collective coordinates (e.g., how the octupole moment is normalized) should be defined explicitly in the text rather than assumed from prior BSkG3 papers.
[Results figures] Figure captions for the barrier and half-life plots would benefit from stating the precise definition of 'primary' barrier used and whether the plotted values include zero-point corrections.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable suggestions. We address the major comments point by point below, indicating where revisions will be made to strengthen the manuscript.

read point-by-point responses

Referee: The central claim that BSkG3 yields usable barriers and half-lives for ~3300 nuclei (including odd/odd-odd systems) rests on the unverified transferability of an EDF previously fitted to ground-state masses and selected deformations. The manuscript does not report a dedicated validation subsection comparing calculated primary barriers against the available experimental fission-barrier data for known heavy nuclei, particularly odd-mass cases; without such benchmarks and quantified discrepancies, the reliability of the extrapolated dataset cannot be assessed.

Authors: We agree that a dedicated validation discussion is important for assessing the reliability of the extrapolated results. Although the BSkG3 functional was primarily fitted to ground-state properties, we will add a new subsection to the revised manuscript that provides a systematic comparison of our calculated primary fission barriers with available experimental data for heavy nuclei. This will include both even-even and odd-mass cases where data are available, with quantified measures such as average deviations and individual case discussions. We believe this will address the concern about transferability. revision: yes
Referee: The least-action principle is invoked to select fission paths, yet the paper provides no explicit test of how the inclusion of triaxial and octupole coordinates alters the action integrals or barriers relative to purely axial calculations for a representative subset of nuclei. This omission is load-bearing because the abstract highlights these coordinates as a key improvement, but their quantitative impact on the final barriers and half-lives is not demonstrated.

Authors: We appreciate this observation. While the full calculations incorporate these coordinates, we acknowledge that an explicit demonstration of their impact would better support the methodological advances claimed. In the revised version, we will include a dedicated analysis for a representative subset of nuclei (covering even-even, odd, and odd-odd systems), comparing the fission barriers and action integrals obtained with axial-only versus triaxial+octupole coordinates. This will be presented in a new figure and text in the methods or results section, quantifying the changes and justifying the inclusion of these degrees of freedom. revision: yes

Circularity Check

0 steps flagged

No circularity: pre-fitted EDF applied to new fission calculations

full rationale

The paper performs large-scale numerical computations of fission barriers and half-lives by applying the existing BSkG3 EDF (with parameters fixed in prior independent work) inside the MOCCa code, using axial/triaxial/octupole coordinates and least-action paths. No equation or result in the present manuscript is obtained by re-fitting parameters to the generated fission data, by self-defining a quantity in terms of itself, or by renaming a prior result as a new derivation. Self-citations to the BSkG3 development papers exist but supply fixed external inputs rather than a load-bearing loop that reduces the central claims to tautology. The work is therefore self-contained as an application study; any concerns about transferability of BSkG3 to fission belong to correctness or validation risk, not circularity.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the established BSkG3 functional and standard nuclear EDF assumptions for collective motion; no new free parameters or invented entities are introduced in the abstract.

axioms (2)

domain assumption The least-action principle identifies the dominant fission path in the chosen collective coordinate space.
Invoked to determine fission paths for all nuclei studied.
domain assumption Axial, triaxial, and octupole moments are sufficient collective coordinates to describe the fission evolution.
Explicitly listed as the deformation degrees of freedom included.

pith-pipeline@v0.9.0 · 5445 in / 1536 out tokens · 55947 ms · 2026-05-07T14:19:29.416807+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

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