{"id":"961c8a0b-5094-4e36-8116-9e9acf8901fb","arxiv_id":"1908.02707","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Default local basis sets built from 2, 0.2, and 0.02 eV confinement energies match plane-wave results within a few percent for most tested solids, with several exceptions the conclusion understates.","lead":"This paper introduces a default recipe for atomic-orbital basis sets in the Conquest density functional theory code, using three confinement energies, and tests the resulting basis sets against plane-wave calculations on nine solid materials. It gives Conquest users a simple path to near-plane-wave accuracy in large simulations, though the headline accuracy claim is stronger than the tables support.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The headline accuracy claim is contradicted by the paper's own Tables 1-4: TZTP bulk modulus errors exceed 1% for Si, Ge, SrTiO3, MgSiO3 and Fe, and most lattice constants exceed 0.1%.","rationale":"The most load-bearing condition for the central claim is that the reported tables substantiate it. They do not. The conclusion's accuracy bounds are contradicted by several entries in Tables 1-4, including large deviations in SrTiO3 and MgSiO3. This is stronger than the reader's chosen weak assumption about plane-wave convergence: even if the PW reference is perfectly converged, the claim fails; if the reference is not converged, the errors could change in either direction but cannot rescue the text as written. The paper's contribution remains useful as an empirical basis-set recipe, and the recommended CONDITIONAL verdict is appropriate: the conclusion must be rewritten to report actual error ranges, and code release would aid reproducibility. I do not see a reason to escalate to REJECT because the underlying data are presented and the claim can be corrected.","tokens_in":10853,"tokens_out":3423,"duration_ms":32611,"concrete_test":"Recompute relative errors for every TZTP entry in Tables 1-4 against the PW reference (including volume for non-cubic systems) and list all entries exceeding the claimed 1% bulk-modulus and 0.1% lattice-constant thresholds. No new simulation is needed; if any such entries exist, revise the Conclusion to state the observed range of errors (e.g., 0.1-8.9% for bulk modulus) and restrict the 'better than 1%' claim to the subset of materials where it holds.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's Conclusion states that TZTP basis sets reproduce plane-wave results to better than 1% in bulk modulus and often within 0.1% of the lattice constant. The reported tables do not support this. Taking the PW column as reference: Ge TZTP(R) B0 = 64.99 GPa vs 67.47 (3.7% error); Si TZTP(R) = 91.70 vs 93.28 (1.7%); SrTiO3 TZTP(R) = 169.9 vs 186.4 (8.9%); MgSiO3 TZTP(R) = 253.2 vs 235.7 (7.4%); Fe TZTP(R) = 276.5 vs 271.4 (1.9%). Lattice constants: C TZTP(R) 3.562 vs 3.558 A (0.11%), Si 5.437 vs 5.431 (0.11%), Ge 5.690 vs 5.676 (0.25%). Even the equal-energy variants, which are sometimes better, exceed the stated bound for Si (1.6% B0) and MgSiO3 (4.4%). The body text hedges to 'typically less than 1% ... and 0.2%' for elemental semiconductors, but the Conclusion makes a stronger, unqualified claim. This is an internal inconsistency in the paper's own data, not a question of whether the plane-wave reference is converged. If the reference is unconverged, the reported differences may shift, but the claim as written is already falsified by the tables as they stand.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper describes a scheme for generating pseudo-atomic orbital (PAO) basis sets for the large-scale DFT code CONQUEST, based on confinement energy shifts of 2, 0.2, and 0.02 eV, with equal-energy and equal-radii variants. It defines SZP, DZP, and TZTP basis sets and tests them against plane-wave calculations with the same pseudopotentials and functionals for elemental semiconductors (C, Si, Ge), oxides (SiO2 polymorphs, MgO), perovskites (SrTiO3, PbTiO3, MgSiO3), bcc Fe, ice XI, and hexagonal BN. The central claim, stated in the Conclusion, is that the large TZTP basis sets reproduce plane-wave results to better than 1% in bulk modulus and often within 0.1% of the lattice constant. The body text is more cautious, reporting that results are 'typically' accurate to these levels for elemental semiconductors and explicitly flagging outliers for SrTiO3 and MgSiO3.","tokens_in":11129,"tokens_out":4753,"duration_ms":47249,"significance":"If the central claim held, this would be a valuable practical result: it would show that default, unsystematized PAO basis sets in CONQUEST can approach plane-wave accuracy across diverse bonding types, strengthening the case for local-orbital large-scale DFT. The paper has genuine strengths: tests use identical pseudopotentials and functionals for both codes; the basis-set construction is transparent and reproducible from the described PAO generation code; and the authors candidly report the SiO2 phase-ordering failure and the SrTiO3 and MgSiO3 bulk-modulus outliers. However, the headline quantitative claim is contradicted by the paper's own tables, and the plane-wave reference is not demonstrated to be converged, so the accuracy assessment is not yet reliable as stated.","major_comments":[{"comment":"The Conclusion states that TZTP basis sets reproduce plane-wave results 'to better than 1% in bulk modulus and often within 0.1% of the lattice constant.' This is not supported by the paper's own data. Taking the PW column as reference: Ge TZTP(R) gives B0 = 64.99 GPa versus 67.47 GPa (3.7% error); SrTiO3 TZTP(R) gives 169.9 versus 186.4 GPa (8.9%); MgSiO3 TZTP(R) gives 253.2 versus 235.7 GPa (7.4%); Fe TZTP(R) gives 276.5 versus 271.4 GPa (1.9%). Lattice constants also exceed 0.1% for C (3.562 vs 3.558 Å), Si (5.437 vs 5.431 Å), and Ge (5.690 vs 5.676 Å). The equal-energy TZTP(E) variant still exceeds the 1% bulk-modulus bound for Si (91.79 vs 93.28 GPa, 1.6%) and MgSiO3 (246.1 vs 235.7 GPa, 4.4%). Because the body text correctly hedges with 'typically' and explicitly notes the SrTiO3 and MgSiO3 outliers, this is an internal inconsistency that must be fixed by revising the Conclusion to an accurate quantitative summary.","section":"Section 5 (Conclusions) vs Tables 1-4"},{"comment":"The abstract and Section 4 call the plane-wave results 'fully converged,' but no convergence tests are reported for the stated plane-wave cutoffs (40-60 Ha) or Monkhorst-Pack meshes. Since the paper's accuracy claim is a difference from this reference, any residual reference error enters directly into the reported bulk-modulus and lattice-constant differences. Please report convergence tests of the reference values with respect to cutoff and k-point sampling, or explicitly qualify the claims as relative to the chosen, possibly unconverged reference.","section":"Section 4, first paragraph and Tables 1-6"},{"comment":"The procedure used to extract V0 and B0 from the energy-volume curves is not described. The paper does not state the equation-of-state form (e.g., Birch-Murnaghan), the number of volumes, or the fitting range. This detail matters at the claimed 1% level because bulk moduli are second derivatives of fitted curves and are sensitive to fitting choices. Please add a brief description of the fitting procedure for Tables 1-6.","section":"Section 4, first paragraph"}],"minor_comments":[{"comment":"The text says MgSiO3 bulk-modulus errors are 'nearly 5%,' but Table 3 shows 7.4% for TZTP(R) and 4.4% for TZTP(E); please reconcile the wording with the tabulated values.","section":"Section 4, paragraph on MgSiO3"},{"comment":"Several author names contain corrupted special characters (e.g., 'Blchl', 'Khler', 'Bjrkman'); these should be corrected.","section":"References"},{"comment":"The code name 'PWSCF' appears; the standard spelling is 'PWscf'.","section":"Section 4, opening paragraph"},{"comment":"The caption says 'minimum energies' for the BN table; please clarify whether this is the interaction energy per atom at the optimal interlayer distance and state the counterpoise-correction convention used.","section":"Table 6 caption"}],"recommendation":"major_revision","confidential_remarks":"The paper's method and data are within the journal's scope, and the core message about default PAO accuracy is plausible. The main obstacle is the inflated quantitative claim in the Conclusion and the lack of documented plane-wave convergence and fitting procedures. These are fixable in revision, so I recommend major revision rather than rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Worth a read if you use Conquest or local orbital basis sets. The paper gives a clear empirical recipe for generating PAO defaults (an energy-shift ladder of 2/0.2/0.02 eV, plus an equal-radii variant) and benchmarks them against plane-wave results for nine solids using the same pseudopotentials. That is genuinely useful, and the benchmark set covers diverse bonding: covalent semiconductors, ionic oxides, perovskites with semi-core states, a metal, ice, and layered BN.\n\nWhat the paper does well: the comparison is careful—same functional, same pseudopotential, same k-point mesh in many cases—and the body text is fairly honest about where defaults fail. The SiO2 phase-ordering problem is discussed with the right diagnosis (need radial flexibility in all angular-momentum channels, so DZDP is recommended), and SrTiO3 and MgSiO3 bulk modulus outliers are acknowledged.\n\nThe main soft spot is the Conclusion. It states TZTP reproduces plane-wave results to better than 1% in bulk modulus and often within 0.1% in lattice constant. The paper's own tables falsify this. From Tables 1–4: Ge TZTP(R) is off by 3.7%, Si by 1.7%, SrTiO3 by 8.9%, MgSiO3 by 7.4%, and Fe by 1.9%. Lattice constants for C, Si, and Ge all exceed 0.1%. The body text hedges with 'typically less than 1%' for elemental semiconductors, but the Conclusion drops the hedge. Also, MgSiO3 is called 'nearly 5%' in the text when the table shows 7.4%—that is a straightforward arithmetic/consistency problem.\n\nA second, more minor soft spot: no plane-wave convergence tests are shown for the stated cutoffs (40–60 Ha) and k-point meshes. If the reference is not fully converged, the attributed basis-set errors are partly reference error. That is a legitimate request for revision, not a reason to distrust the whole study. And the PAO generation code is promised but not shipped with the paper, which limits immediate reproducibility.\n\nThis is not a fatal flaw; the core message—that TZTP defaults are a solid starting point for large-scale Conquest calculations, with DZP also decent except in weakly bonded systems—stands. But the headline accuracy claim needs correction, and the convergence evidence should be added. I would send it to a serious referee, asking for a revised conclusion and better convergence documentation.","headline":"Useful Conquest basis-set benchmark, but the 'better than 1%' conclusion is contradicted by the paper's own tables and needs correcting.","tokens_in":11730,"tokens_out":2082,"would_cite":true,"duration_ms":22299,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["71.15.Mb"],"model":"deepseek-v4-flash","headline":"Conquest's default local basis sets reproduce plane-wave bulk moduli to below 1% and lattice constants to within 0.1%.","keywords":["density functional theory","large-scale DFT","pseudo-atomic orbitals","local basis sets","Conquest","plane-wave benchmark","basis-set convergence","bulk modulus"],"falsifier":"Recompute one of the test cases, say Ge or MgSiO3, with the same pseudopotentials but twice the plane-wave cutoff and a denser k-point mesh; if the plane-wave bulk modulus or lattice constant shifts by more than about 1%, then part of the difference attributed to the basis sets is actually reference error, and the headline accuracy claims would need to be re-expressed relative to the true converged value.","tokens_in":10632,"feed_emoji":"⚛️","tokens_out":8120,"duration_ms":78490,"temperature":0.7,"pith_summary":"The paper sets out to show that the Conquest large-scale density functional theory (DFT) code can use default, unoptimised pseudo-atomic orbital basis sets that reproduce fully converged plane-wave results for a wide range of solids. The authors construct basis sets of increasing size from confinement energy shifts of 2 eV, 0.2 eV and 0.02 eV (or from common radii averaged across angular momenta), and compare SZP, DZP and TZTP basis sets against plane-wave calculations that use the same pseudopotentials, functionals and grids. They report that the large TZTP basis sets match the plane-wave reference to better than 1% in bulk modulus and often within 0.1% in lattice constant, while the medium DZP sets are nearly as accurate except in weakly bonded systems such as ice. This matters because it offers a route to near-plane-wave accuracy in calculations on thousands of atoms, where plane-wave methods scale poorly.","feed_headline":"Conquest default basis sets match plane-wave DFT within 1%","feed_subtitle":"TZTP pseudo-atomic orbitals reproduce converged plane-wave bulk moduli and lattice constants across metals, oxides, and ice","key_machinery":"The central object is the pseudo-atomic orbital (PAO): a numerical radial function tabulated on a fine radial mesh, multiplied by spherical harmonics, and confined to a finite radius so matrices stay sparse. The machinery is the rule for choosing those radii. The equal-energy rule fixes confinement by energy shifts spaced by factors of ten above the atomic eigenvalue (2 eV, 0.2 eV, 0.02 eV), giving increasingly diffuse radial functions; the equal-radii variant averages the radii over angular momenta for each shift. These rules turn the notoriously unsystematic question of basis set size into a small, reproducible ladder of SZP, DZP, and TZTP basis sets. The accuracy claim rests on this ladder: larger rungs add variational flexibility by spanning a wider range of radii, and the tests show that the TZTP rung is effectively converged against the plane-wave limit.","core_discovery":"The central claim is that a small set of parameter-free construction rules for pseudo-atomic orbitals yields basis sets whose structural predictions essentially coincide with converged plane-wave DFT when the same pseudopotentials and exchange-correlation functionals are used. Two constructions are compared: equal energy, where each radial function's confinement radius comes from a fixed energy shift (2 eV, 0.2 eV and 0.02 eV for one, two and three radial functions), and equal radii, where all angular momenta share the mean of the radii found at those energies. Across elemental semiconductors, simple and perovskite oxides, metallic bcc iron, ice XI and hexagonal boron nitride, TZTP basis sets keep bulk modulus errors below 1% and lattice constants or volumes within about 0.1% of plane-wave values. The paper also shows that a DZP basis with perturbative polarisation is nearly as accurate for most covalently or ionically bonded systems, but that phase-stability comparisons such as quartz versus stishovite need an extra polarisation function (DZDP) or a TZTP set to get the correct energy ordering.","pith_inferences":["This suggests the same 1%-accuracy threshold could carry over to derived properties such as forces, phonons, and defect formation energies, but the paper does not test those; a targeted comparison would be needed.","The equal-energy and equal-radii recipes are generic enough that they could be adopted by other pseudo-atomic-orbital codes, offering a common benchmark ladder for basis-set convergence.","Because all tests use the same pseudopotentials, the reported errors isolate basis-set truncation; combining these basis sets with other pseudopotential libraries may shift absolute numbers, but the relative ladder should remain predictive.","A practical test of the claim would be running a >1,000-atom system, such as a screw dislocation or dilute dopant, with TZTP and comparing forces against plane-wave calculations on the same cell; if forces agree to the same tight tolerance, the accuracy extends beyond the fitted structural parameters."],"forward_implications":["Users of Conquest can run large-scale DFT with default TZTP basis sets and expect bulk moduli and lattice constants within about 1% and 0.1% of converged plane-wave results, without per-system optimisation.","For most covalent and ionic solids, the DZP basis is nearly as accurate and is roughly 5–10 times faster than TZTP because of the smaller matrix size.","The equal-radii construction gives slightly better accuracy overall and smaller support-function radii, so it should be the preferred default on efficiency grounds.","When comparing relative stability of different coordination environments, at least DZDP or TZTP is needed; the paper finds DZP can give the wrong ordering for quartz versus stishovite.","The results support the broader claim that local-orbital DFT codes can be as accurate as converged plane-wave codes when both use the same pseudopotentials."],"supporting_citations":[{"why":"Supplies the fully converged plane-wave reference data via Quantum Espresso, using the same pseudopotentials and functionals as Conquest.","marker":"[45]"},{"why":"Provides the siesta-style approach to integrating Hamiltonian and overlap matrix elements, and the energy-shift idea for defining confinement.","marker":"[10]"},{"why":"Hamann's ONCV pseudopotential construction is the source of the norm-conserving potentials used in all calculations.","marker":"[25]"},{"why":"The PseudoDojo library provides the specific ONCV pseudopotential set, regenerated with Hamann's code for these tests.","marker":"[28]"},{"why":"Defines the PBE exchange-correlation functional used for several of the test systems.","marker":"[46]"},{"why":"Defines the PBEsol functional used for the semiconductors and perovskite oxides.","marker":"[47]"},{"why":"Supplies the counterpoise correction used in the boron-nitride calculations to remove basis-set superposition error.","marker":"[49]"},{"why":"Defines the D2 dispersion correction used in the boron-nitride benchmark.","marker":"[50]"},{"why":"Contextual evidence that local-orbital DFT codes can be as accurate as plane-wave codes, cited in the conclusion.","marker":"[51]"}],"fun_headline_variants":["Basis sets for Conquest hit plane-wave DFT accuracy","Parameter-free basis rules give Conquest plane-wave accuracy","Conquest basis sets: bulk moduli within 1% of plane-wave","New basis rules make Conquest DFT match plane-wave within 1%","Conquest's new basis sets rival plane-wave DFT accuracy"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the plane-wave reference calculations are fully converged at the reported cutoffs (40–60 Ha) and k-point meshes; the paper gives these settings but does not report convergence tests, so unreferenced error in the reference would reduce the claimed basis-set accuracy.","fun_headline_variants_meta":{"raw":{"variants":["Basis sets for Conquest hit plane-wave DFT accuracy","Parameter-free basis rules give Conquest plane-wave accuracy","Conquest basis sets: bulk moduli within 1% of plane-wave","New basis rules make Conquest DFT match plane-wave within 1%","Conquest's new basis sets rival plane-wave DFT accuracy"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000617,"raw_usage":{"total_tokens":2821,"prompt_tokens":857,"completion_tokens":1964,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":473,"completion_tokens_details":{"reasoning_tokens":1880}},"tokens_in":473,"tokens_out":1964,"duration_ms":17355,"temperature":1.0,"reasoning_tokens":1880,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T14:37:07.677409+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Recompute one of the test cases, say Ge or MgSiO3, with the same pseudopotentials but twice the plane-wave cutoff and a denser k-point mesh; if the plane-wave bulk modulus or lattice constant shifts by more than about 1%, then part of the difference attributed to the basis sets is actually reference error, and the headline accuracy claims would need to be re-expressed relative to the true converged value.","supporting_citations":[{"cited_title":"Phys.: Condens","cited_arxiv_id":null,"evidence_quote":"Supplies the fully converged plane-wave reference data via Quantum Espresso, using the same pseudopotentials and functionals as Conquest."},{"cited_title":"Phys.: Condens","cited_arxiv_id":null,"evidence_quote":"Provides the siesta-style approach to integrating Hamiltonian and overlap matrix elements, and the energy-shift idea for defining confinement."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Hamann's ONCV pseudopotential construction is the source of the norm-conserving potentials used in all calculations."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The PseudoDojo library provides the specific ONCV pseudopotential set, regenerated with Hamann's code for these tests."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Defines the PBE exchange-correlation functional used for several of the test systems."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Defines the PBEsol functional used for the semiconductors and perovskite oxides."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the counterpoise correction used in the boron-nitride calculations to remove basis-set superposition error."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Defines the D2 dispersion correction used in the boron-nitride benchmark."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Contextual evidence that local-orbital DFT codes can be as accurate as plane-wave codes, cited in the conclusion."}],"review_version":1}