• Volume 1, Issue 3-4

      December 1979,   pages  129-240

    • Soft modes and structural phase transitions

      G Venkataraman

      More Details Abstract Fulltext PDF

      This paper presents a survey of soft modes and their relationship to structural phase transitions. After introducing the concept of a soft mode, the origin of softening is considered from a lattice-dynamical point. The Landau theory approach to structural transitions is then discussed, followed by a generalisation of the soft-mode concept through the use of the dynamic order-parameter susceptibility. The relationship of soft modes to broken symmetry is also examined. Experimental results for several classes of crystals are next presented, bringing out various features such as the co-operative Jahn-Tellev effect. The survey concludes with a discussion of the central peak, touching upon both the experimental results and the theoretical speculations.

    • Some characteristics of first-order phase transformations

      V Raghavan

      More Details Abstract Fulltext PDF

      The distinction between first-order and second-order phase transformations is brought out. The general characteristics of first-order transformations are described. The salient features of transformations controlled by long-range diffusion, short-range diffusion and by (diffusionless) shear mechanisms are discussed. Martensitic trasnformations, which belong to the shear category, occur in many metallic and non-metallic systems and deserve an intensive study.

    • The phenomenon of glass transition

      K J Rao

      More Details Abstract Fulltext PDF

      Principal features of glass transition phenomenon are summarised. Various theoretical approaches such as free volume, entropy, energy surface, etc., have been briefly discussed.

    • Slow relaxation in spin glasses

      B Sriram Shastry

      More Details Abstract Fulltext PDF

      The remarkable remanence effects observed in spin glasses are discussed. Some theoretical approaches and results are reviewed.

    • Critical properties of random magnetic systems

      Deepak Kumar

      More Details Abstract Fulltext PDF

      A review of the recent applications of renormalisation group techniques to the calculations of the critical properties of random magnetic systems is presented.

    • One-dimensional conductors

      S V Subramanyam

      More Details Abstract Fulltext PDF

      A brief review of one-dimensional conductors with emphasis on the synthetic criterion, the model systems of radical ion salts, charge transfer complexes, metal chain systems, polymeric conductors and A3B compounds is given.

    • Critical phenomena in solids

      V Shubha

      More Details Abstract Fulltext PDF

      In general a solid-solid phase boundary does not terminate in a critical point due to symmetry requirements. However, there exists systems like pure cerium metal and rare earth compounds like samarium sulphide where an isostructural solid-solid phase boundary terminates at a critical point. The critical point for the pressure-induced semiconductor-metal phase transition in SmS has been determined for the first time using the thermoelectric power data collected upto 12 kbar pressure and 850° C. These results are discussed on the basis of some theoretical models developed for the mixed valent compounds.

    • Order-disorder transition in ammonium copper chloride dihydrate

      V C Sahni

      More Details Abstract Fulltext PDF

      The nature of the NH4 network in the order-disorder transition of ammonium copper chloride dehydrate is examined.

    • Nonequilibrium phase transitions

      S Dattagupta

      More Details Abstract Fulltext PDF

      A brief review is provided of the subject of nonequilibrium phase transitions occurring in various systems in different disciplines. All these systems exhibit a similar kind of ordering phenomena at a macroscopic level and can therefore be classified in terms of appropriate order parameters. Typical order parameter equations are discussed in the light of Landau’s phenomenological theory of phase transitions. The instabilities occurring in a few chemical reactions are discussed in some detail and the role of fluctuations pointed out. Mention is also made of the possibility of viewing some metallurgical phenomena as examples of nonequilibrium phase transitions.

  • Bulletin of Materials Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.