Mechanical properties of layered tilkerodeite (Pd2HgSe3) and jacutingaite (Pt2HgSe3) crystals: Insights on the interlayer, intralayer interactions, and phonons

Abstract

Tilkerodeite and jacutingaite are layered minerals promising for low-power nano-spintronic devices due to their robust topological phases and air stability. Their intralayer and interlayer mechanical properties, of paramount importance for real applications, are here unveiled by first-principles calculations. Their stiffness coefficients, which confirm their lattice stability, and interlayer force constants show that tilkerodeite is weaker against intralayer deformations, slightly difficult to exfoliate, and less lubricant than jacutingaite. Jacutingaite aggregates are more stiff, incompressible, and resistant to shape-change deformations than tilkerodeite, while the latter is more ductile than the former. The wavenumber shifts between corresponding vibration modes in these materials show that tilkerodeite is less stiff than jacutingaite against the atomic displacement of optical silent, infrared- and Raman-active modes, while the opposite was found for their low-frequency breathing and shear rigid-layer modes. Our findings advance the knowledge on the structural properties of new quantum spin Hall materials, key for their use, and explained the unexpected wavenumber redshift of the tilkerodeite Raman spectrum relative to that of jacutingaite observed in experiments.

Raman and Far-Infrared Synchrotron Nanospectroscopy of Layered Crystalline Talc: Vibrational Properties, Interlayer Coupling, and Symmetry Crossover

“…81 In the case of the interlayer breathing force constant (K LMB ), we found 6.55 × 10 19 N m −3 , which is about 28% smaller than that in graphene, 76 and about 45 and 52% greater than that in β-GaSe and ε-GaSe, 77 respectively, and about 65% smaller than that in jacutingaite and tilkerodeite minerals. 81 These results agree with the fact that talc can be easily exfoliated and is an excellent lubricant. 27,38,42 Finally, we extract the talc interlayer stiffness coefficients against interlayer shear movement along armchair-and zigzaglike directions and against strain perpendicular to the layers, given by 4.0, 37.5, and 59.3 GPa, respectively.…”

“…The in-plane anisotropy for the shear movement is about 840%, showing that talc should slide preferentially in the armchair direction in comparison to the zigzag. The K LSM along the armchair direction in talc is about 66% smaller than that in graphene and GaSe and about 91% smaller than that in jacutingaite and tilkerodeite minerals . The K LSM along the zigzag direction in talc is about 218% greater than that in graphene and GaSe and about 20% smaller than that in jacutingaite and tilkerodeite minerals .…”

“…The K LSM along the armchair direction in talc is about 66% smaller than that in graphene and GaSe 77 and about 91% smaller than that in jacutingaite and tilkerodeite minerals. 81 The K LSM along the zigzag direction in talc is about 218% greater than that in graphene 76 and GaSe 77 and about 20% smaller than that in jacutingaite and tilkerodeite minerals. 81 In the case of the interlayer breathing force constant (K LMB ), we found 6.55 × 10 19 N m −3 , which is about 28% smaller than that in graphene, 76 and about 45 and 52% greater than that in β-GaSe and ε-GaSe, 77 respectively, and about 65% smaller than that in jacutingaite and tilkerodeite minerals.…”

“…81 The K LSM along the zigzag direction in talc is about 218% greater than that in graphene 76 and GaSe 77 and about 20% smaller than that in jacutingaite and tilkerodeite minerals. 81 In the case of the interlayer breathing force constant (K LMB ), we found 6.55 × 10 19 N m −3 , which is about 28% smaller than that in graphene, 76 and about 45 and 52% greater than that in β-GaSe and ε-GaSe, 77 respectively, and about 65% smaller than that in jacutingaite and tilkerodeite minerals. 81 These results agree with the fact that talc can be easily exfoliated and is an excellent lubricant.…”

“…The low-frequency rigid-layer modes in LMs can be rationalized by the application of a linear-chain model. 8,[74][75][76][77][78]80,81 By fitting the linear-chain model to our calculation results (red line in Figure 8), we can obtain the interlayer force constants of layered talc, from bulk to the 2L regime. We find that the interlayer force constant for shear movement (K LSM ) along the armchair-and zigzag-like directions are 0.44 × 10 19 and 4.14 × 10 19 N m −3 , respectively.…”