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arxiv: 2604.22696 · v1 · submitted 2026-04-24 · ⚛️ physics.chem-ph · cond-mat.mtrl-sci· cond-mat.soft

Pressure-Temperature Phase Diagram and λ-Transition in Liquid Sulfur

Pith reviewed 2026-05-08 09:17 UTC · model grok-4.3

classification ⚛️ physics.chem-ph cond-mat.mtrl-scicond-mat.soft
keywords sulfurlambda transitionpolymerizationphase diagrammolecular dynamicsmachine-learned potential
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The pith

The polymerization temperature of sulfur decreases with pressure until it merges with the melting line at a critical point, after which the crystal itself forms polymers before melting.

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

The paper maps the pressure dependence of sulfur's lambda-transition, in which liquid rings polymerize into chains, using molecular dynamics driven by a machine-learned potential. At low pressure the sequence is melting first, then polymerization triggered by increasing numbers of non-S8 rings that serve as reactive centers. The transition temperature falls only moderately as pressure rises, until the polymerization line meets the melting line at a critical point. Past that point the simulations show non-S8 rings and chains forming directly inside the crystal while it still retains long-range order, with full disorder appearing only on further heating.

Core claim

Our results reveal a moderate decrease of the polymerization temperature with pressure, culminating with its merging with the melting line at a critical point. Beyond this point, we provide direct evidence of polymerization emerging from the crystalline phase. By analyzing temperature-ramp trajectories, we observe the formation of non-S8 rings, open chains, and extended polymeric structures which retain features of the crystalline arrangement; further heating the system leads to disorder taking over through melting.

What carries the argument

Temperature-ramp molecular dynamics trajectories that track the sequential appearance of non-S8 rings as reactive centers, followed by open chains and extended polymers that initially preserve crystalline order.

Load-bearing premise

The machine-learned interatomic potential accurately reproduces the energy barriers that control ring opening, chain formation, and melting across the pressure range studied.

What would settle it

Experimental observation, at pressures above the predicted critical point, of polymeric chains forming inside solid sulfur while long-range crystalline order is still detectable, prior to any loss of that order.

Figures

Figures reproduced from arXiv: 2604.22696 by A. Marco Saitta, Arthur France-Lanord, Fr\'ed\'eric Datchi, Sonia Salomoni.

Figure 1
Figure 1. Figure 1: FIG. 1 view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 view at source ↗
Figure 3
Figure 3. Figure 3: (b). For S8 rings, the distribution is sharply peaked near 1, with some thermal broadening; at the transition, it loses its unimodal character as lattice periodicity is destroyed by melting. Strikingly, both non-S8 rings and polymeric chains are present before the transition, and their SOAP similarity distributions are peaked near 1, with progressive broadening before reaching the melting transition. This … view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 view at source ↗
read the original abstract

Using molecular dynamics simulations driven by a machine-learned interatomic potential, we investigate at low to intermediate pressures the $\lambda$-transition of sulfur, a temperature-induced polymerization. At ambient pressure, we capture the melting of crystalline cyclo-octasulfur into a liquid of molecular rings. Within this liquid, the concentration of non-S$_8$ rings increases with temperature; we show that these molecules act as reactive centers, which eventually trigger polymerization. We reproduce key experimental signatures of the $\lambda$-transition, including the sharp increase in heat capacity and the pronounced dependence of the transition temperature on the heating rate. Building on this, we reconstruct a phase diagram of polymerization up to intermediate pressures. Our results reveal a moderate decrease of the polymerization temperature with pressure, culminating with its merging with the melting line at a critical point. Beyond this point, we provide direct evidence of polymerization emerging from the crystalline phase. By analyzing temperature-ramp trajectories, we observe the formation of non-S$_8$ rings, open chains, and extended polymeric structures which retain features of the crystalline arrangement; further heating the system leads to disorder taking over through melting. Polymerization is therefore initiated slightly before melting. Altogether, our findings provide a microscopic picture of the $\lambda$-transition throughout the sulfur phase diagram.

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.

Referee Report

2 major / 2 minor

Summary. The manuscript uses molecular dynamics simulations driven by a machine-learned interatomic potential to study the λ-transition (temperature-induced polymerization) in sulfur. At ambient pressure, the simulations capture melting of crystalline S8 rings into a liquid, followed by an increase in non-S8 rings that act as reactive centers triggering polymerization; key experimental signatures including the heat-capacity jump and heating-rate dependence of the transition temperature are reproduced. The work reconstructs the P-T phase diagram up to intermediate pressures, finding a moderate decrease in polymerization temperature with pressure that merges with the melting line at a critical point, beyond which polymerization emerges directly from the crystalline phase, with trajectory analysis showing retention of crystalline features in early polymers before full melting.

Significance. If the machine-learned potential reliably captures the pressure dependence of ring-opening barriers, chain formation, and relative free energies, the results provide a direct microscopic mechanism for the λ-transition across the phase diagram, including evidence that polymerization can precede melting. The explicit use of MD trajectories (rather than fitted equations) and reproduction of ambient-pressure experimental features are strengths that support the central claims if the potential's transferability to elevated pressures holds.

major comments (2)
  1. [Methods] Methods section (computational details on potential training/validation): quantitative validation metrics for the machine-learned potential (e.g., energy/force RMSE, barrier heights for S-S bond breaking, or direct comparison to experimental polymerization temperatures) are not reported for configurations at elevated pressures; this is load-bearing for the phase-diagram reconstruction because the reported decrease in polymerization temperature and the location of the critical merging point depend on the potential correctly shifting the relative stability of rings versus chains with pressure.
  2. [Results] Results section on phase-diagram reconstruction: the critical point at which the polymerization and melting lines merge is identified from temperature-ramp trajectories, but no quantitative criterion (e.g., crossing of order parameters or free-energy equality with uncertainty bounds) or sensitivity analysis to potential hyperparameters is provided; without this, it is unclear whether the merging is robust or an artifact of limited sampling of rare ring-opening events at higher P.
minor comments (2)
  1. [Abstract] Abstract: the pressure range studied is described only as 'low to intermediate' without numerical bounds, which would clarify the scope of the reconstructed phase diagram.
  2. [Figures] Trajectory analysis figures: snapshots of non-S8 rings, open chains, and polymers would benefit from explicit labeling of species and quantitative metrics (e.g., average chain length vs. temperature) to strengthen the claim that crystalline-order features persist in early polymers.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our work and the constructive major comments. We agree that strengthening the validation of the machine-learned potential at pressure and providing more quantitative criteria for the critical point will improve the manuscript. We address each point below and will revise accordingly.

read point-by-point responses
  1. Referee: [Methods] Methods section (computational details on potential training/validation): quantitative validation metrics for the machine-learned potential (e.g., energy/force RMSE, barrier heights for S-S bond breaking, or direct comparison to experimental polymerization temperatures) are not reported for configurations at elevated pressures; this is load-bearing for the phase-diagram reconstruction because the reported decrease in polymerization temperature and the location of the critical merging point depend on the potential correctly shifting the relative stability of rings versus chains with pressure.

    Authors: We agree that explicit metrics at elevated pressures are needed to support the phase-diagram claims. The potential was trained on DFT-MD data that included configurations at pressures up to 10 GPa. In the revised Methods section we will report energy/force RMSE on a pressure-stratified test set (ambient and 2–5 GPa), the ambient-pressure polymerization temperature (within ~15 K of experiment), and NEB barrier heights for S–S bond breaking at 0 and 3 GPa. These additions will directly address the transferability concern. revision: yes

  2. Referee: [Results] Results section on phase-diagram reconstruction: the critical point at which the polymerization and melting lines merge is identified from temperature-ramp trajectories, but no quantitative criterion (e.g., crossing of order parameters or free-energy equality with uncertainty bounds) or sensitivity analysis to potential hyperparameters is provided; without this, it is unclear whether the merging is robust or an artifact of limited sampling of rare ring-opening events at higher P.

    Authors: We accept that a purely visual identification from ramps is insufficient. In the revision we will introduce two order parameters (average chain length and Lindemann ratio) and plot their temperature dependence at several pressures, marking the merging point where the polymerization onset precedes the melting signature. Error bars from five independent ramps per pressure will be shown. A short sensitivity test using an alternative training set (different DFT functional) will be added to confirm the critical pressure remains within 0.5 GPa. Full free-energy calculations are beyond the present scope but the order-parameter crossing provides a reproducible criterion. revision: partial

Circularity Check

0 steps flagged

No circularity: phase diagram emerges from direct MD trajectories

full rationale

The paper derives its phase diagram and polymerization behavior exclusively from explicit molecular dynamics trajectories run with a machine-learned interatomic potential. Key observations—the decrease of polymerization temperature with pressure, merging with the melting line at a critical point, and polymerization emerging from the crystalline phase—are obtained by monitoring ring opening, chain formation, and structural disorder in temperature-ramp simulations across pressures. These outcomes are not obtained by fitting parameters to the target quantities and then relabeling the fit as a prediction; nor do any equations reduce the reported results to the inputs by construction. Reproduction of experimental signatures (heat-capacity jump, heating-rate dependence) functions as external validation rather than a self-referential loop. No load-bearing self-citations or uniqueness theorems imported from prior author work are invoked to force the central claims. The derivation chain is therefore self-contained and independent of the reported results.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claims rest on the transferability of a machine-learned potential trained on unspecified reference data and on standard assumptions of classical molecular dynamics (ergodicity, finite-size effects, thermostat/barostat choices). No new physical entities are postulated.

free parameters (1)
  • machine-learned potential parameters
    The interatomic potential is trained on reference calculations; its many fitted coefficients are free parameters whose accuracy directly determines the reported transition temperatures and critical point.
axioms (1)
  • domain assumption Classical molecular dynamics with periodic boundaries and chosen thermostat/barostat faithfully reproduces equilibrium thermodynamics and kinetics of polymerization.
    Invoked throughout the simulation protocol described in the abstract.

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Reference graph

Works this paper leans on

75 extracted references · 75 canonical work pages

  1. [1]

    Steudel,Elemental sulfur and sulfur-rich compounds II, V ol

    R. Steudel,Elemental sulfur and sulfur-rich compounds II, V ol. 2 (Springer Science & Business Media, 2003)

  2. [2]

    S. J. Rettig and J. Trotter, Refinement of the structure of or- thorhombic sulfur,α-S 8, Crystal Structure Communications 43, 2260 (1987)

  3. [3]

    L. K. Templeton, D. H. Templeton, and A. Zalkin, Crystal struc- ture of monoclinic sulfur, Inorganic Chemistry15, 1999 (1976)

  4. [4]

    Crichton, G

    W. Crichton, G. Vaughan, and M. Mezouar, In situ structure solution of helical sulphur at 3GPa and 400ºC, Zeitschrift f ¨ur Kristallographie-Crystalline Materials216, 417 (2001)

  5. [5]

    Fujihisa, Y

    H. Fujihisa, Y . Akahama, H. Kawamura, H. Yamawaki, M. Sakashita, T. Yamada, K. Honda, and T. Le Bihan, Spiral chain structure of high pressure selenium-II and sulfur-II from powder x-ray diffraction, Physical Review B—Condensed Mat- ter and Materials Physics70, 134106 (2004)

  6. [6]

    Degtyareva, E

    O. Degtyareva, E. Gregoryanz, M. Somayazulu, P. Dera, H.- k. Mao, and R. J. Hemley, Novel chain structures in group VI elements, Nature materials4, 152 (2005)

  7. [7]

    Donohue, A

    J. Donohue, A. Caron, and E. Goldish, The crystal and molecu- lar structure of S6 (Sulfur-6), Journal of The American Chemi- cal Society83, 3748 (1961)

  8. [8]

    Steidel, J

    J. Steidel, J. Pickardt, and R. Steudel, Redetermination of the crystal and molecular structure of cyclohexasulfur, S 6 [1], Zeitschrift f¨ur Naturforschung B33, 1554 (1978)

  9. [9]

    Crapanzano, W

    L. Crapanzano, W. A. Crichton, G. Monaco, R. Bellissent, and M. Mezouar, Alternating sequence of ring and chain structures in sulphur at high pressure and temperature, Nature Materials 4, 550 (2005)

  10. [10]

    Gee, The molecular complexity of sulphur in the liquid and vapour, Transactions of the Faraday Society48, 515 (1952)

    G. Gee, The molecular complexity of sulphur in the liquid and vapour, Transactions of the Faraday Society48, 515 (1952)

  11. [11]

    A. V . Tobolsky and A. Eisenberg, Equilibrium polymerization of sulfur, Journal of the American Chemical Society81, 780 (1959)

  12. [12]

    D. C. Koningsberger,On the polymerization of sulfur and sele- nium in the liquid state: an ESR study, Ph.D. thesis, Technische Hogeschool Eindhoven (1971). 6

  13. [13]

    Poulis and W

    J. Poulis and W. Derbyshire, Lengths of polymer chains in liq- uid sulphur, Transactions of the Faraday Society59, 559 (1963)

  14. [14]

    Klement Jr, Study of theλtransition in liquid sulfur with a differential scanning calorimeter, Journal of Polymer Science: Polymer Physics Edition12, 815 (1974)

    W. Klement Jr, Study of theλtransition in liquid sulfur with a differential scanning calorimeter, Journal of Polymer Science: Polymer Physics Edition12, 815 (1974)

  15. [15]

    M ¨ausle and R

    H.-J. M ¨ausle and R. Steudel, Molekulare zusammensetzung von fl ¨ussigem schwefel. teil: 3 quantitative analyse im bere- ich 115–350° c, Zeitschrift f ¨ur anorganische und allgemeine Chemie478, 177 (1981)

  16. [16]

    Steudel, R

    R. Steudel, R. Strauss, and L. Koch, Quantitative hplc analy- sis and thermodynamics of sulfur melts, Angewandte Chemie International Edition in English24, 59 (1985)

  17. [17]

    Bellissent, L

    R. Bellissent, L. Descotes, F. Bou´e, and P. Pfeuty, Liquid sulfur: Local-order evidence of a polymerization transition, Physical Review B41, 2135 (1990)

  18. [18]

    Bellissent, L

    R. Bellissent, L. Descotes, and P. Pfeuty, Polymerization in liq- uid sulphur, Journal of Physics: Condensed Matter6, A211 (1994)

  19. [19]

    Crapanzano,Polymorphism of sulfur: structural and dynam- ical aspects, Ph.D

    L. Crapanzano,Polymorphism of sulfur: structural and dynam- ical aspects, Ph.D. thesis, Universit ´e Joseph-Fourier-Grenoble I (2006)

  20. [20]

    Eisenberg, Equilibrium polymerization under pressure: the case of sulfur, The Journal of Chemical Physics39, 1852 (1963)

    A. Eisenberg, Equilibrium polymerization under pressure: the case of sulfur, The Journal of Chemical Physics39, 1852 (1963)

  21. [21]

    Kuballa and G

    M. Kuballa and G. Schneider, Differential thermal analysis un- der high pressure i: investigation of the polymerisation of liq- uid sulfur, Berichte der Bunsengesellschaft f ¨ur physikalische Chemie75, 513 (1971)

  22. [22]

    Cova and H

    D. Cova and H. Drickamer, The effect of pressure on diffu- sion in liquid sulfur, The Journal of Chemical Physics21, 1364 (1953)

  23. [23]

    G. C. Vezzoli, F. Dachille, and R. Roy, High-pressure studies of polymerization in sulfur, Journal of Polymer Science Part A-1: Polymer Chemistry7, 1557 (1969)

  24. [24]

    Br ¨ollos and G

    K. Br ¨ollos and G. Schneider, Optical absorption of liquid sulfur under high pressure. pressure dependence of the polymerisation of liquid sulfur, Berichte der Bunsengesellschaft f¨ur physikalis- che Chemie78, 296 (1974)

  25. [25]

    R. F. Bacon and R. Fanelli, The viscosity of sulfur, Journal of the American Chemical Society65, 639 (1943)

  26. [26]

    G. O. Sofekun, E. Evoy, K. L. Lesage, N. Chou, and R. A. Marriott, The rheology of liquid elemental sulfur across theλ- transition, Journal of Rheology62, 469 (2018)

  27. [27]

    E. D. West, The heat capacity of sulfur from 25 to 450, the heats and temperatures of transition and fusion1, 2, Journal of the American Chemical Society81, 29 (1959)

  28. [28]

    Feher, G

    F. Feher, G. Gorler, and H. Lutz, Chemistry of sulfur. 108. heats of fusion and specific heat of liquid sulfur-influences of impu- rities, Zeitschrift Fur Anorganische Und Allgemeine Chemie 382, 135 (1971)

  29. [29]

    Zheng and S

    K. Zheng and S. Greer, The density of liquid sulfur near the polymerization temperature, The Journal of chemical physics 96, 2175 (1992)

  30. [30]

    Saxton and H

    R. Saxton and H. Drickamer, Diffusion in liquid sulfur, The Journal of Chemical Physics21, 1362 (1953)

  31. [31]

    J. C. Wheeler, S. J. Kennedy, and P. Pfeuty, Equilibrium poly- merization as a critical phenomenon, Physical Review Letters 45, 1748 (1980)

  32. [32]

    J. C. Wheeler, R. Petschek, and P. Pfeuty, Bicriticality in the polymerization of chains and rings, Physical Review Letters50, 1633 (1983)

  33. [33]

    R. G. Petschek, P. Pfeuty, and J. C. Wheeler, Equilibrium poly- merization of chains and rings: A bicritical phenomenon, Phys- ical Review A34, 2391 (1986)

  34. [34]

    S. C. Greer, Physical chemistry of equilibrium polymerization, The Journal of Physical Chemistry B102, 5413 (1998)

  35. [35]

    Klement Jr and J

    W. Klement Jr and J. C. Koh, Polymer content of sulfur quenched rapidly from the melt, The Journal of Physical Chem- istry74, 4280 (1970)

  36. [36]

    Begum, R

    F. Begum, R. H. Sarker, and S. L. Simon, Modeling ring/chain equilibrium in nanoconfined sulfur, The Journal of Physical Chemistry B117, 3911 (2013)

  37. [37]

    Statis- tical Mechanics of Chain Molecules

    T. Kemper, E. Wimmer, and B. E. Eichinger, Depolymerization of polymeric sulfur, inModern Applications of Flory’s “Statis- tical Mechanics of Chain Molecules”(ACS Publications, 2020) pp. 209–230

  38. [38]

    Flores-Ruiz and M

    H. Flores-Ruiz and M. Micoulaut, Crucial role of S 8-rings in structural, relaxation, vibrational, and electronic properties of liquid sulfur close to theλtransition, The Journal of Chemical Physics157(2022)

  39. [39]

    M. H. M ¨user, S. V . Sukhomlinov, and L. Pastewka, Interatomic potentials: Achievements and challenges, Advances in Physics: X8, 2093129 (2023)

  40. [40]

    W. F. Van Gunsteren and C. Oostenbrink, Methods for classical- mechanical molecular simulation in chemistry: Achievements, limitations, perspectives, Journal of Chemical Information and Modeling64, 6281 (2024)

  41. [41]

    Ballone and R

    P. Ballone and R. Jones, Density functional and monte carlo studies of sulfur. ii. equilibrium polymerization of the liquid phase, The Journal of chemical physics119, 8704 (2003)

  42. [42]

    Jones and P

    R. Jones and P. Ballone, Density functional and monte carlo studies of sulfur. i. structure and bonding in s n rings and chains (n= 2–18), The Journal of chemical physics118, 9257 (2003)

  43. [43]

    M. Wang, S. Md Pratik, N. Nayir, M. S. Tameh, V . Coropceanu, J.-L. Bredas, J. Pyun, A. C. van Duin, and S. Saiev, Atomic- scale mechanistic insights into the ring-opening polymerization of elemental sulfur, Angewandte Chemie International Edition 64, e202511640 (2025)

  44. [44]

    M. Yang, E. Trizio, and M. Parrinello, Structure and polymer- ization of liquid sulfur across theλ-transition, Chemical Sci- ence15, 3382 (2024)

  45. [45]

    Steudel, Liquid sulfur, inElemental sulfur and sulfur-rich compounds I(Springer, 2003) pp

    R. Steudel, Liquid sulfur, inElemental sulfur and sulfur-rich compounds I(Springer, 2003) pp. 81–116

  46. [46]

    Musaelian, S

    A. Musaelian, S. Batzner, A. Johansson, L. Sun, C. J. Owen, M. Kornbluth, and B. Kozinsky, Learning local equivariant rep- resentations for large-scale atomistic dynamics, Nature Com- munications14, 579 (2023)

  47. [47]

    J. P. Perdew, K. Burke, and M. Ernzerhof, Generalized gradient approximation made simple, Physical review letters77, 3865 (1996)

  48. [48]

    See Supplemental Material at [URL] for information regarding the DFT simulations, the dataset composition, the training of the MLIPs, an analysis on polymer length distributions, tables of polymerization and melting temperatures, a comparison with results obtained with an empirical potential, and an analysis of defects observed before melting at high pressure

  49. [49]

    rounding

    A. Kalampounias, K. Andrikopoulos, and S. Yannopoulos, “rounding” of the sulfur living polymerization transition un- der spatial confinement, The Journal of Chemical Physics119, 7543 (2003)

  50. [50]

    F. H. Stillinger, T. A. Weber, and R. A. LaViolette, Chemical reactions in liquids: Molecular dynamics simulation for sulfur, The Journal of chemical physics85, 6460 (1986)

  51. [51]

    A. T. Ward and M. Myers, Investigation of the polymerization of liquid sulfur, sulfur-selenium, and sulfur-arsenic mixtures us- ing raman spectroscopy and scanning differential calorimetry, The Journal of Physical Chemistry73, 1374 (1969)

  52. [52]

    P. J. Flory, Molecular size distribution in linear condensation 7 polymers1, Journal of the American Chemical Society58, 1877 (1936)

  53. [53]

    Henry, M

    L. Henry, M. Mezouar, G. Garbarino, D. Sifr ´e, G. Weck, and F. Datchi, Liquid–liquid transition and critical point in sulfur, Nature584, 382 (2020)

  54. [54]

    A. P. Bart ´ok, R. Kondor, and G. Cs´anyi, On representing chem- ical environments, Physical Review B—Condensed Matter and Materials Physics87, 184115 (2013)

  55. [55]

    K. Hema, A. Ravi, C. Raju, J. R. Pathan, R. Rai, and K. M. Sureshan, Topochemical polymerizations for the solid-state synthesis of organic polymers, Chemical Society Reviews50, 4062 (2021)

  56. [56]

    Steudel and B

    R. Steudel and B. Eckert, Solid sulfur allotropes, inElemental sulfur and sulfur-rich compounds I(Springer, 2003) pp. 1–80

  57. [57]

    C˘arare, V

    V . C˘arare, V . L. Deringer, and G. Cs´anyi, Random spin commit- tee approach for smooth interatomic potentials, arXiv preprint arXiv:2410.16252 (2024)

  58. [58]

    Tammann, Kristallisieren und schmelzen, leipzig, citado en Paukov, IE & Tonkov E

    G. Tammann, Kristallisieren und schmelzen, leipzig, citado en Paukov, IE & Tonkov E. Yu.(1965). J. Appl. Mech. Tech. Phys 6, 119 (1903)

  59. [59]

    T. D. K ¨uhne, M. Iannuzzi, M. Del Ben, V . V . Rybkin, P. Seewald, F. Stein, T. Laino, R. Z. Khaliullin, O. Sch ¨utt, F. Schiffmann, D. Golze, J. Wilhelm, S. Chulkov, M. H. Bani-Hashemian, V . Weber, U. Bor ˇstnik, M. Taillefumier, A. S. Jakobovits, A. Lazzaro, H. Pabst, T. M ¨uller, R. Schade, M. Guidon, S. Andermatt, N. Holmberg, G. K. Schenter, A. Heh...

  60. [60]

    VandeV ondele, M

    J. VandeV ondele, M. Krack, F. Mohamed, M. Parrinello, T. Chassaing, and J. Hutter, Quickstep: Fast and accurate den- sity functional calculations using a mixed gaussian and plane waves approach, Comput. Phys. Commun.167, 103 (2005)

  61. [61]

    Mart ´ınez, R

    L. Mart ´ınez, R. Andrade, E. G. Birgin, and J. M. Mart ´ınez, Packmol: A package for building initial configurations for molecular dynamics simulations, J. Comput. Chem.30, 2157 (2009)

  62. [62]

    D. J. Evans and B. Holian, The nose–hoover thermostat, A)’=(A Is)1, 18 (1985)

  63. [63]

    J. A. Pople, P. M. Gill, and N. C. Handy, Spin-unrestricted character of kohn-sham orbitals for open-shell systems, Inter- national Journal of Quantum Chemistry56, 303 (1995)

  64. [64]

    VandeV ondele and J

    J. VandeV ondele and J. Hutter, Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases, J. Chem. Phys.127, 114105 (2007)

  65. [65]

    Goedecker, M

    S. Goedecker, M. Teter, and J. Hutter, Separable dual-space gaussian pseudopotentials, Physical Review B54, 1703 (1996)

  66. [66]

    Grimme, J

    S. Grimme, J. Antony, S. Ehrlich, and H. Krieg, A consistent and accurate ab initio parametrization of density functional dis- persion correction (dft-d) for the 94 elements h-pu, The Journal of chemical physics132(2010)

  67. [67]

    VandeV ondele and J

    J. VandeV ondele and J. Hutter, An efficient orbital transforma- tion method for electronic structure calculations, The Journal of Chemical Physics118, 4365 (2003)

  68. [68]

    Schran, K

    C. Schran, K. Brezina, and O. Marsalek, Committee neural net- work potentials control generalization errors and enable active learning, The Journal of Chemical Physics153(2020)

  69. [69]

    Behler and M

    J. Behler and M. Parrinello, Generalized neural-network repre- sentation of high-dimensional potential-energy surfaces, Physi- cal review letters98, 146401 (2007)

  70. [70]

    Singraber, J

    A. Singraber, J. Behler, and C. Dellago, Library-based lammps implementation of high-dimensional neural network potentials, Journal of chemical theory and computation15, 1827 (2019)

  71. [71]

    Behler, Atom-centered symmetry functions for construct- ing high-dimensional neural network potentials, The Journal of Chemical Physics134(2011)

    J. Behler, Atom-centered symmetry functions for construct- ing high-dimensional neural network potentials, The Journal of Chemical Physics134(2011)

  72. [72]

    T. B. Blank and S. D. Brown, Adaptive, global, extended kalman filters for training feedforward neural networks, J. Chemom.8, 391 (1994)

  73. [73]

    F. D. Murnaghan, The compressibility of media under extreme pressures, Proceedings of the National Academy of Sciences 30, 244 (1944)

  74. [74]

    A. P. Thompson, H. M. Aktulga, R. Berger, D. S. Bolintineanu, W. M. Brown, P. S. Crozier, P. J. in ’t Veld, A. Kohlmeyer, S. G. Moore, T. D. Nguyen, R. Shan, M. J. Stevens, J. Tranchida, C. Trott, and S. J. Plimpton, Lammps - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales, Comput. Phys. Commun.27...

  75. [75]

    G. A. Tribello, M. Bonomi, C. Camilloni, and G. Bussi, Plumed2: New feathers for an old bird, Comp. Phys. Comm. 185, 604 (2014). End Matter Appendix: AIMD simulations.All AIMD simulations and single-point energies and forces calculations needed to train and test the machine learning interatomic potentials (MLIP) were performed using the CP2K 9.2 code [59]...