Phase diagram of the triangular Ising model: Renormalization-group calculation with application to adsorbed monolayers

摘要: We study a triangular Ising model subject to nearest-neighbor pair interactions $K$, an external magnetic field $H$, and three-spin $P$. $Kg0 (l0)$ corresponds ferromagnetic (antiferromagnetic) coupling. The phase diagram thermodynamics are invariant under $(K,H,P)\ensuremath{\leftrightarrow}(K,\ensuremath{-}H,\ensuremath{-}P)$. A simple position-space renormalization group is formulated, based on three interpenetrating cells, which preserves the three-sublattice symmetry of antiferromagnetic phase. complete ($K,H,P$) consists five interconnecting transition surfaces (two second-order first-order), bound four single-phase regions (\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\uparrow}, \ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}, \ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\downarrow}, \ensuremath{\downarrow}\ensuremath{\downarrow}\ensuremath{\downarrow}). edges these form loci second-order, critical-endpoint, Baxter-Wu transitions. When $P=0$, this system known provide useful order-disorder in monolayer films adsorbed hexagonal substrate. Calculation magnetization $M(K,H)$ heat capacity ${c}_{M}(K,H)$ allows quantitative comparison with experimental data for helium graphite. observed dependence ${T}_{c}(n)$ temperature coverage well fit single effective interaction. corresponding calculated capacities (no additional adjustable parameters) remarkable agreement near below ${T}_{c}$.