• • A crystallographic orientation difference >10° between contacting 2H-WS2 grains at 1000 °C reduces the heterogeneous nucleation energy barrier for the 1T phase to 0.005 eV, compared to 2.314 eV for homogeneous nucleation—a 463-fold reduction—enabling spontaneous phase transformation at the contact boundary without catalysts or intercalants.
• • The thermodynamic stability of 2H- and 1T-WS2 reverses at 280 K; above this threshold, 1T-WS2 becomes the stable phase, providing a clear temperature window for selective synthesis of the metallic phase in industrial processes operating at elevated temperatures.
• • The transformation proceeds via an interface-mediated mechanism: lattice mismatch at large-angle boundaries induces defects and lattice distortion, triggering atomic rearrangement that converts the contact region to 1T-WS2, which then propagates through adjacent 2H nanosheets, ultimately yielding large-area, phase-pure 1T-WS2 films.
• • The process uses only 2H-WS2 nanosheets as the raw material and requires no intercalation agents or organic solvents, eliminating contamination risks and simplifying purification, which is critical for catalytic and electronic applications where residual impurities degrade performance.