Skip to content

Multi-physics predictive framework for thermolysis of titanium(IV)-isopropoxide

Summary

The study builds a multi-tier workflow—DLPNO-CCSD(T)/B3LYP QM, ReaxFF reparameterization for Ti/C/O/H chemistry of titanium(IV) isopropoxide (TTIP), AMS ReaxFF-MD sampling of isolated and condensed TTIP scenarios, and metadynamics (PLUMED-style enhanced sampling referenced in Methods)—to map ligand-separation pathways beyond a sole β-hydride elimination picture for CVD/MBE-relevant TTIP pyrolysis.

Methods

  • QM reference: DLPNO-CCSD(T) with cc-pVTZ plus B3LYP/cc-pVTZ zero-point energies (ORCA), following Eq. (1) in the paper for composite energies.
  • ReaxFF training: Starting from prior Ti/C/O/H ReaxFF sets; refit Ti–O bond, C–O–Ti / O–Ti–O / Ti–O–H angles, and H–C–O–Ti / C–O–Ti–O dihedrals with Ti–C and Ti–H covalent terms disabled (nonbonded only), minimizing squared error to QM pathways for β-hydride, β-X/C–O, and β-X/Ti–O categories.
  • ReaxFF-MD (AMS): Molecular dynamics in Amsterdam Modeling Suite (AMS) with reactive ReaxFF; fifty replica copies of isolated TTIP in 100×100×100 Å\(^3\) 3D PBC periodic gas boxes (~O(100) atoms per molecule in each replica); NVT ensemble, Δt = 0.25 fs, Berendsen thermostat (100 fs damping); 1×10\(^6\)-step equilibration at 300 K, 1×10\(^6\)-step ramp to 2000 K, then 8×10\(^6\)-step production at 2000 K to accelerate kinetics (experimental CVD 700–1300 K). Additional batches: TTIP with H, H\(_2\), H\(_2\)O; 25-molecule condensed cells with repeats as in the PDF.
  • Metadynamics: PLUMED-driven metadynamics along C–O and Ti–O collective variables (see Methods/Supplement) to obtain barrier-linked kinetics vs ReaxFF-MD counts. N/A — static external electric field; N/A — isotropic 1 bar NPT in the high-T gas runs summarized (use NVT).

Findings

  • First ligand separation is mostly C–O cleavage (~74% of ReaxFF-MD cases), with ~20% Ti–O cleavage; β-hydride elimination accounts for ~38% of C–O subset cases—showing C–O scission is not synonymous with β-hydride only.
  • β-X channels (alkyl/alkoxy releases) appear with substantial frequency alongside classical β-hydride paths; later ligand removals show shifting dominance between C–O and Ti–O cleavage, with Ti–O episodes often gated to maintain Ti valence balance.
  • Metadynamics and QM together rank some Ti–O vs C–O barriers differently than intuition from simplified β-hydride schemes; kinetic ratios η(T) (paper Fig. 11) show temperature-dependent switches in whether C–O or Ti–O pathways dominate for successive ligand removals.

Limitations

Accelerated 2000 K gas-phase MD trades experimental temperatures for observable kinetics; authors note need for more replicas to tighten pre-exponentials for quantitative Arrhenius predictions.

Relevance to group

Fazlıoğlu-Yalçın, Nayir, van Duin, and collaborators: multi-physics TTIP thermolysis with QM, ReaxFF, and metadynamics for oxide CVD/MBE contexts.

Citations and evidence anchors

Reader notes (navigation)

These sections summarize what the checked-in extraction and abstracts support; they are not a substitute for the full PDF. For theme-level retrieval, see paper-index-by-domain and hubs linked from canonical_tags in the front matter above. Operators updating chunks should reconcile numbers with normalized/extracts/ and the version-of-record PDF when available.