PACS 64.70.K--Solid-solid transitions PACS 64.60.De -Statistical mechanics of model systems (Ising model, Potts model, field-theory models, Monte Carlo techniques, etc.

Quinoxaline, quinazoline and benzimidazole based templates have been synthesized on solid-support employing different methodologies. This review enlightens academic and industrial examples of combinatorial synthesis for this type of heterocycles that appeared in the literature in the last decade. Hence, some of the important synthetic strategies for the generation of quinoxaline, quinazoline and benzimidazole based privileged structures, and the important biological activities for these heterocycles have been highlighted. Further, benzothiadiazinone, thioxoquinazolinone, cinnoline and indazole are also examined in this review.

We study martensitic transition kinetics through temperature-quench Monte Carlo simulations for a square/rectangle ferroelastic transition, described by a Hamiltonian of three-state pseudospins S, without extrinsic disorder. Here S = 0 for high-temperature austenite, and S = ±1 for the two martensite variants. The temperaturedependent pseudospin Hamiltonian comes from the total scaled free energy functional, evaluated at the three minima of Landau polynomials in order-parameter strains. It includes power-law anisotropic interactions from the St. Venant compatibility constraint, which orient the elastic domain walls in a symmetry-breaking diagonal direction. We find that temperature-time-transformation (TTT) plots for domain-wall phase evolution have phase crossover temperatures, which are understood through an effective-droplet energy parametrization. For temperature cycling through the phases, there are hysteretic peaks in physical quantities. For temperature quenches, a "vapor" of martensitic droplets converts at a time t m (T ) to a vibrating "liquid" of bidiagonal domain walls, which then orient at a time t C (T ) to a static "crystal" of single-diagonal martensitic twins, which can have bound residual austenite. Focusing on the conversion time t m , we find a material-parameter phase diagram, which has regions of nonactivated "athermal" and activated "isothermal" martensites. In an athermal, nonactivated regime, there are explosive austenite-martensite conversions at temperatures below a residual-austenite spinodal in the TTT diagram, while above it, there are conversion tails, as in experiment. We find t m (T ) has a quasi-universal Vogel-Fulcher divergence at transition, with a log-normal conversion-rate distribution. The incubation times t m , t C are attributed to entropy barriers, with signatures of flat energies, during pathway searches for finite-scale transition textures, which are explicitly identified through textural and internal-stress snapshots. In a glasslike energy landscape picture, these entropic pathways to many locked-twin states dominate those to a single-variant martensite state, of almost the same energy density. Other transitions in 2D and 3D can be similarly studied. More generally, the models could be used to explore conceptual issues of how systems equilibrate after a deep quench.

We present systematic temperature-quench Monte Carlo simulations on discrete-strain pseudospin model Hamiltonians to study microstructural evolutions in 2D ferroelastic transitions with twocomponent vector order parameters (NOP = 2). The zero value pseudospin is the single hightemperature phase while the low-temperature phase has Nv variants. Thus the number of nonzero values of pseudospin are triangle-to-centered rectangle (Nv = 3), square-to-oblique (Nv = 4) and triangle-to-oblique (Nv = 6). The model Hamiltonians contain a transition-specific Landau energy term, a domain wall cost or Ginzburg term, and power-law anisotropic interaction potential, induced from a strain compatibility condition. On quenching below a transition temperature, we find behaviour similar to the previously studied square-to-rectangle transition (NOP = 1, Nv = 2), showing that the rich behaviour found, is generic. Thus we find for two-component order parameters, that the same Hamiltonian can describe both athermal and isothermal martensite regimes for different material parameters. The athermal/isothermal/austenite parameter regimes and temperature-timetransformation diagrams are understood, as previously, through parametrization of effective-droplet energies. In the athermal regime, we find rapid conversions below a spinodal like temperature and austenite-martensite conversion delays above it, as in the experiment. The delays show early incubation behaviour, and at the transition to austenite the delay times have Vogel-Fulcher divergences and are insensitive to Hamiltonian energy scales, suggesting that entropy barriers are dominant.

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