{"id":"c1408b64-1ac5-4dc3-8154-ff43fe2467a3","arxiv_id":"2505.24359","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Direct DFT node searches change the predicted nodal counts for TaIrTe4, SrSi2, and the Cu2XY3 family, including finding no Weyl points or nodal arcs in Cu2SnTe3.","lead":"This study rechecks three families of topological materials using direct density-functional calculations instead of the Wannier tight-binding models used in earlier predictions. It reports extra Weyl points in TaIrTe4 and SrSi2, and finds that several Cu2XY3 materials have different or no topological features than previously predicted.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The claimed node counts are not exhaustive: PY-NODE is run only on the topmost-valence/bottommost-conduction band pair, so 'sixteen Weyl nodes' and 'no Weyl points' are lower bounds for one band pair, not the full band structure.","rationale":"The reader's weakest_assumption identifies the same load-bearing concern: the node search is restricted to the touching point between the topmost valence band and the bottommost conduction band, so the paper's exhaustive-sounding counts are not established. This is the central issue because the abstract and conclusions state corrected counts and a negative result for Cu2SnTe3, and those statements rely on the search having covered all relevant band pairs. The concern does not by itself falsify the reported findings for the searched pair; it makes the current evidence incomplete. The authors could resolve it with an all-pairs search on the same Hamiltonians, which is computationally feasible. I therefore keep the reader's CONDITIONAL verdict rather than escalating to REJECT. Secondary issues — missing raw data, no explicit PY-NODE convergence tests, and possible differences in lattice parameters between this work and previous studies — reinforce the conditional status but are not the primary structural flaw.","tokens_in":11481,"tokens_out":5138,"duration_ms":69844,"concrete_test":"Run PY-NODE (or an equivalent all-pairs node finder) on the same converged DFT Hamiltonians for TaIrTe4 and Cu2SnTe3 for all band pairs within, say, ±1 eV of the Fermi energy, using identical k-mesh and tolerances. If additional Weyl points or nodal lines appear outside the topmost-valence/bottommost-conduction pair, then the reported counts are incomplete and the central claim against prior tight-binding-model results must be re-evaluated. The test should also report convergence of node coordinates and energies with k-mesh density and with the number of minimization starting seeds.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The TaIrTe4 section states that 'PY-NODE code successfully identified the touching point between the topmost valence band and the bottommost conduction band across the full Brillouin zone' and then reports 'a total of sixteen Weyl nodes and two nodal lines.' The Cu2XY3 section repeats the same restriction: 'we performed calculations to identify the touching points in the full Brillouin zone between the topmost valence band and the bottommost conduction band.' Because the search is confined to one band pair, any Weyl point or nodal line formed by lower valence or higher conduction bands is invisible to the scan. The headline corrections — four extra Weyl points in TaIrTe4, 24 nodes in SrSi2, and zero nodes in Cu2SnTe3 — are presented as complete counts of the material's topological nodes, but they are at most counts for the selected pair. In a multi-band semimetal other pairs can cross; the claim 'did not find any Weyl points' for Cu2SnTe3 is therefore not established. This is not a numerical quibble: it limits what the central comparison can prove. The paper shows that PY-NODE finds or does not find nodes in one band pair, not that the tight-binding-model predictions about the material's full topology are wrong.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript revisits the topological classification of TaIrTe4, SrSi2, and the Cu2XY3 family (X=Si, Ge, Sn; Y=S, Se, Te) using direct DFT-based searches for band crossings with the PY-NODE code and chirality checks with WloopPHI. The authors report additional Weyl points in TaIrTe4 and SrSi2 relative to earlier tight-binding studies, and a null result for Weyl points in Cu2SnTe3, and they argue that MLWF-based tight-binding models are unreliable. They also study the sensitivity of the Cu2SnS3 topological phase to atomic displacements. The central claims are presented as corrections to published topological assignments.","tokens_in":11716,"tokens_out":14515,"duration_ms":153848,"significance":"If the reported node counts were established as exhaustive, the paper would provide an important cautionary result for the use of Wannier-interpolated tight-binding models in topological materials discovery. The use of a full-potential DFT search with explicit chirality verification is a methodological strength, and the node coordinates and energies in Tables I and II are falsifiable predictions. However, the exhaustiveness of the node search and the internal consistency of the Cu2XY3 results must be resolved before the conclusions can be accepted.","major_comments":[{"comment":"The PY-NODE search is explicitly restricted to the touching point between the topmost valence band and the bottommost conduction band. Consequently, the reported counts—'sixteen Weyl nodes' for TaIrTe4, '24 node points' for SrSi2, and 'did not find any Weyl points' for Cu2SnTe3—are at most lower bounds for a single band pair, not exhaustive counts of all Weyl nodes in the material. Because the paper uses these counts to overturn earlier full-band-structure tight-binding predictions, either the search must be extended to all band pairs or the claims must be rephrased as pair-restricted results.","section":"Topological nature of TaIrTe4; Verification of topological phase of Cu2XY3"},{"comment":"The text contains a direct contradiction: it first states that 'the materials Cu2GeSe3, Cu2GeTe3, and Cu2SnSe3 host eight, eight, and four Weyl points, respectively,' and then states that 'In the case of Cu2SnSe3 and Cu2SnTe3, we did not find any Weyl points or nodal rings.' The abstract only claims the null result for Cu2SnTe3, so at least one of these statements is erroneous. Please correct the text and ensure the SM tables are consistent.","section":"Verification of topological phase of Cu2XY3"},{"comment":"The topological assignments for the Cu2XY3 family differ between the abstract and the main text. The abstract assigns 'four small nodal rings, eight Weyl points, and eight nodal arcs, respectively' to Cu2SiTe3, Cu2GeTe3, and Cu2GeSe3, whereas the main text gives eight Weyl points to Cu2GeSe3 and assigns the eight nodal arcs to Cu2GeS3 (introduced parenthetically). These conflicting assignments must be reconciled before the paper can be understood consistently.","section":"Abstract; Verification of topological phase of Cu2XY3"},{"comment":"The attribution of the differences to 'inaccuracy of the constructed TBM' or 'limitations in the Wannierization procedure' is not supported by the evidence presented, because the authors do not control for differences in DFT code, lattice constants, XC functional, or other numerical settings between their calculations and those of Refs. [14,17,47]. A controlled comparison, such as constructing Wannier functions from the same DFT calculation, is needed before concluding that Wannierization is the source of the discrepancies.","section":"Introduction; Topological nature of TaIrTe4"},{"comment":"No convergence analysis is reported for the PY-NODE search with respect to k-mesh, smearing width, or number of bands, and no error estimates are given for the node coordinates and energies in Tables I and II. The Introduction itself stresses the need for such convergence; without it, the quantitative node positions and energies are not yet established to the standard the paper advocates.","section":"Computational details; Tables I and II"},{"comment":"The newly identified W2 nodes in SrSi2 are obtained only with the PBE/PBEsol functionals; the same section reports that with TB-mBJ at the near-experimental lattice constant (6.5106 Å) a gap of 11.14 meV opens, so no Weyl nodes exist at that level of theory. The abstract's unqualified statement that additional Weyl points were found in SrSi2 therefore overstates the case; the sensitivity to the XC functional and lattice constant should be reflected in the abstract.","section":"Topological nature of SrSi2; Abstract"}],"minor_comments":[{"comment":"The text states a 1% reduction of the optimized lattice parameter gives ≈6.5106 Å; however, 6.5698 Å × 0.99 = 6.5041 Å, so the stated percentage and value are inconsistent. Please correct the percentage or the numerical value.","section":"Topological nature of SrSi2"},{"comment":"The sentence 'Cu2SiTe3 (Cu2GeS3) hosts four small nodal rings (eight nodal-arcs)' is ambiguous; please spell out the assignment for each material separately.","section":"Verification of topological phase of Cu2XY3"},{"comment":"The SM is cited for 'Table IV' in two different contexts (band gaps for SrSi2 and nodal features for Cu2XY3), which suggests a table-numbering conflict in the supplementary material; please verify the SM numbering.","section":"Topological nature of SrSi2; Verification of topological phase of Cu2XY3"},{"comment":"The statement that at 6.5106 Å 'the topmost valence band crosses the Fermi level' is followed immediately by 'within this potential, there is a band gap of 11.14 meV' for the same lattice constant; please clarify which functional each statement refers to.","section":"Topological nature of SrSi2"},{"comment":"Table I lists only the three representative sets W1–W3; since the claim is sixteen Weyl nodes, please state the multiplicities explicitly (e.g., number of points per set) or list all sixteen points.","section":"Table I"},{"comment":"There are minor typos, such as 'materail' in the last paragraph of the SrSi2 section, and inconsistent use of 'nodal arcs' versus 'nodal rings' between the abstract and the main text.","section":"Throughout"}],"recommendation":"major_revision","confidential_remarks":"The paper presents a useful methodological caution, but the current manuscript has several load-bearing inconsistencies that need careful revision. The dependence of the conclusions on the restricted band-pair search and the internal contradictions in the Cu2XY3 section are the most serious issues. The reliance on the authors' own prior benchmarks for PY-NODE and WloopPHI is a further concern that the editor may wish to weigh when assessing the novelty and independence of the validation."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: the paper reports concrete, checkable corrections to published topological counts for three material families using direct DFT searches rather than Wannier tight-binding. That is a genuinely useful exercise, and the authors do some things well: they list coordinates and energies for nodes, check chirality with WloopPHI, test multiple functionals and lattice parameters for SrSi2, and include a sensible robustness study for Cu2SnS3. The central idea—that structural sensitivity and exchange-correlation choice can explain theory-experiment mismatches—is plausible.\n\nThe soft spot is real and it is not minor. The PY-NODE search is explicitly limited to the touching point between the topmost valence band and the bottommost conduction band, in every material section. The text then presents \"sixteen Weyl nodes\" for TaIrTe4, \"24 nodes\" for SrSi2, and \"no Weyl points\" for Cu2SnTe3 as if they were complete counts of the material's topology. They are not. Other band pairs can cross in a multi-band semimetal, and the paper provides no argument that the relevant physics lives only in that one pair. So the headline corrections are, at best, statements about one band pair. That does not destroy the paper's value, but it changes the claim from \"the earlier TBM predictions are wrong\" to \"the earlier predictions are not reproduced for this specific pair with these settings.\" That is still worth publishing, but the abstract and conclusions need to say it.\n\nOther issues: no k-mesh or smearing convergence analysis, no error bars on node energies, and the TaIrTe4 table appears incomplete relative to the text—it lists only W1/W2/W3 rather than all 16 nodes. The reliance on the authors' own PY-NODE code, without convergence data in this paper, is a related weakness; citing your own earlier benchmarks is fine, but here the benchmark citations are doing work that a convergence section should do. None of this sinks the project, but it matters for how confident the reader can be in the numbers.\n\nWho is this for? People who work on these specific materials, and anyone using TBM-derived topological catalogs. A serious referee should see it, mainly to enforce the band-pair restriction and ask for convergence data. If I were the editor, I would send it out.","headline":"A useful corrective study whose headline node counts are undercut by an unstated band-pair restriction; worth refereeing, but the completeness claims need reining in.","tokens_in":12272,"tokens_out":2312,"would_cite":false,"duration_ms":30497,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Direct DFT node searches correct published Weyl-node counts in TaIrTe4, SrSi2, and the Cu2XY3 family.","keywords":["Weyl semimetal","nodal lines","nodal rings","first-principles DFT","tight-binding model","TaIrTe4","SrSi2","Cu2XY3"],"falsifier":"Repeat the node search on the same compounds while scanning lower valence and higher conduction bands; finding additional Weyl nodes in Cu2SnTe3, or more than sixteen in TaIrTe4, would falsify the paper's stated counts. A simpler check is to reproduce the TaIrTe4 and Cu2SnTe3 counts with an independent all-electron DFT code and successively denser k-meshes.","tokens_in":11228,"feed_emoji":"⚛️","tokens_out":4578,"duration_ms":52645,"temperature":0.7,"pith_summary":"Using direct density-functional-theory node searches rather than Wannier-function-based tight-binding models, this paper re-examines three families of predicted topological semimetals and finds that published node counts change. It reports sixteen Weyl nodes and two nodal lines in TaIrTe4 (four nodes more than earlier studies), a previously missing set of twelve Weyl pairs in SrSi2, and no Weyl points or nodal rings in Cu2SnTe3, contrary to a recent tight-binding prediction. The paper argues that such differences help explain why experimental checks of topological-phase catalogs sometimes come up empty, because small changes in lattice parameters, atomic positions, or the exchange-correlation functional can move or destroy the nodes. A sympathetic reader would take the central claim to be that direct first-principles band-touching searches are the more reliable benchmark for these materials.","feed_headline":"DFT node search overturns Weyl-node tallies in three materials","feed_subtitle":"TaIrTe4 and SrSi2 gain nodes, Cu2SnTe3 loses them, and strain shifts the phase.","key_machinery":"The load-bearing tool is a direct first-principles search for band-touching points (the paper's PY-NODE code) that uses Nelder-Mead minimization on DFT bands to find where the topmost valence band and the bottommost conduction band touch across the full Brillouin zone, with chiralities checked by a Wilson-loop calculation. The comparison target is the maximally localized Wannier-function tight-binding model used in prior studies. The argument works by showing that the direct search finds nodes the tight-binding model misses, or finds none where the model predicted nodes, and by showing that the result is sensitive to lattice constants, atomic positions, and the exchange-correlation functional.","core_discovery":"The central discovery is a set of corrected topological node counts obtained by searching directly on DFT band structure instead of on a fitted tight-binding model. In TaIrTe4, the direct search finds sixteen Weyl points and two nodal lines, with four of the Weyl points absent from earlier studies. In SrSi2, the same approach yields three distinct sets of Weyl points, W1, W2, and W3, where the W2 set (twelve pairs) was not reported in prior work. In the Cu2XY3 family, the paper finds four small nodal rings in Cu2SiTe3, eight Weyl points in Cu2GeTe3, eight Weyl points in Cu2GeSe3, and no Weyl points or nodal rings in Cu2SnTe3, each differing from published tight-binding results. The paper further shows that the SrSi2 gap depends sensitively on the functional and lattice constant, and that in Cu2SnS3 small atomic displacements can drive the Weyl phase into a nodal-arc phase.","pith_inferences":["Because the search only examines the topmost valence and bottommost conduction bands, the corrected counts may still be incomplete; a full all-band search could reveal additional nodes deeper in the band structure.","The same direct-search re-benchmarking could be applied to other materials whose topological status rests on Wannier-function tight-binding models, and would likely yield different counts for some of them.","The sensitivity of node existence to lattice constants and functionals suggests that topological-phase maps should be published as phase diagrams over strain and band filling, not as single-lattice verdicts.","A testable extension would be to check whether the newly found W2 nodes in SrSi2 and the extra four nodes in TaIrTe4 produce surface Fermi-arc signatures distinct from the previously known nodes."],"forward_implications":["Published tight-binding counts for TaIrTe4, SrSi2, and the Cu2XY3 family should be treated with caution until confirmed by direct DFT node searches.","Corrected counts: TaIrTe4 hosts sixteen Weyl points and two nodal lines; SrSi2 has an additional twelve-pair Weyl set W2; Cu2SnTe3 is not a Weyl semimetal.","SrSi2 sits near a topological transition: at the experimental lattice constant it is metallic within PBE, gapped within TB-mBJ, and develops Weyl nodes under roughly 1.5% compression, so samples with slightly different lattice constants can appear semimetallic or semiconducting.","In Cu2SnS3, atomic displacements of order 0.01 to 0.03 can switch the system from a Weyl phase to a nodal-arc phase, so local strain in real samples can wash out predicted topological signatures."],"supporting_citations":[{"why":"the tight-binding prediction that TaIrTe4 hosts only four Weyl points, the baseline this paper overturns","marker":"[14]"},{"why":"the ARPES study reporting four Weyl points in TaIrTe4","marker":"[15]"},{"why":"the combined study reporting twelve Weyl points and two nodal lines in TaIrTe4, four fewer than found here","marker":"[17]"},{"why":"the earlier SrSi2 study that reported W1 and W3, whose missing W2 set this paper adds","marker":"[40]"},{"why":"the PY-NODE direct first-principles node-search code used for all the band-touching searches","marker":"[43]"},{"why":"the tight-binding prediction for the Cu2XY3 class whose Weyl-point and nodal-ring counts this paper contradicts","marker":"[47]"},{"why":"the WIEN2k DFT code used for all electronic structure calculations","marker":"[48]"},{"why":"the PBE exchange-correlation functional used for the self-consistent calculations","marker":"[49]"},{"why":"the Wilson-loop code used to compute Weyl-point chiralities","marker":"[53]"}],"fun_headline_variants":["DFT rerun fixes Weyl-node counts in TaIrTe4, SrSi2, and Cu2XY3","Corrected Weyl counts: TaIrTe4 and SrSi2 gain, Cu2SnTe3 loses","Direct DFT search finds missing Weyl points in TaIrTe4 and SrSi2","Strain shifts topological phase in Cu2SnS3","Cu2SnTe3 has no Weyl points, unlike prior predictions"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The search is limited to the touching point between the topmost valence band and the bottommost conduction band, so any Weyl point or nodal line involving other bands would be missed, even though the paper reports its node counts as complete.","fun_headline_variants_meta":{"raw":{"variants":["DFT rerun fixes Weyl-node counts in TaIrTe4, SrSi2, and Cu2XY3","Corrected Weyl counts: TaIrTe4 and SrSi2 gain, Cu2SnTe3 loses","Direct DFT search finds missing Weyl points in TaIrTe4 and SrSi2","Strain shifts topological phase in Cu2SnS3","Cu2SnTe3 has no Weyl points, unlike prior predictions"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001465,"raw_usage":{"total_tokens":5955,"prompt_tokens":1066,"completion_tokens":4889,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":682,"completion_tokens_details":{"reasoning_tokens":4775}},"tokens_in":682,"tokens_out":4889,"duration_ms":37000,"temperature":1.0,"reasoning_tokens":4775,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T12:25:05.602512+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Repeat the node search on the same compounds while scanning lower valence and higher conduction bands; finding additional Weyl nodes in Cu2SnTe3, or more than sixteen in TaIrTe4, would falsify the paper's stated counts. A simpler check is to reproduce the TaIrTe4 and Cu2SnTe3 counts with an independent all-electron DFT code and successively denser k-meshes.","supporting_citations":[{"cited_title":"Thunstr¨ om and K","cited_arxiv_id":null,"evidence_quote":"the tight-binding prediction that TaIrTe4 hosts only four Weyl points, the baseline this paper overturns"},{"cited_title":"Koepernik, D","cited_arxiv_id":null,"evidence_quote":"the ARPES study reporting four Weyl points in TaIrTe4"},{"cited_title":"Belopolski, P","cited_arxiv_id":null,"evidence_quote":"the combined study reporting twelve Weyl points and two nodal lines in TaIrTe4, four fewer than found here"},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"the earlier SrSi2 study that reported W1 and W3, whose missing W2 set this paper adds"},{"cited_title":"Mele, Proc","cited_arxiv_id":null,"evidence_quote":"the PY-NODE direct first-principles node-search code used for all the band-touching searches"},{"cited_title":"Pandey and S","cited_arxiv_id":null,"evidence_quote":"the tight-binding prediction for the Cu2XY3 class whose Weyl-point and nodal-ring counts this paper contradicts"},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"the WIEN2k DFT code used for all electronic structure calculations"}],"review_version":1}