Size,Dimensionality,Composition And Interface Effects On Melting Temperature Of Low Dimensionality

Nanocrystals,stemming from their low dimensionality,have been widely used in various fields.Owing to their large surface-to-volume ratio,nanocrystals exhibit novel characteristics different from those of their bulk counterparts.Among the novel properties of nanocrystals,melting is a common phenomenon in our daily life and is an important topic in condensed matter physics,material science and other disciplines.The melting temperature of nanocrystals can be tailored by manipulating the size,dimensionality,composition and interface.In addition,as the existing the direct or indirect relationships between melting temperature and some basic properties,the present investigation can be considered a bridge to investigate these properties of nanocrystals.Therefore,understanding the melting behavior of nanocrystals not only can give the guidance to predict the thermal stability of nanocrystals under the given conditions,but also can derive other physical and chemical properties.The investigation of the melting behaviors of nanocrystals can deepen our understanding of the underlying mechanisms and aid the design and application of efficient future nanodevices.With the development of device miniaturization,the thermal stability of nanocrystals becomes a crucial issue to be considered for practical applications.Therefore,it is necessary to comprehensively understand the melting behaviors of nanocrystals and to reveal the mechanisms underlying.In this paper,a thermodynamic model is established to describe the size,dimensionality,composition and interface effects on melting temperature.In addition,the established model has been extended to predict Debye temperature of nanocrystals.The accuracy of the established model is verified via comparisons of its predictions with available experimental data and simulation results.The content can be divided into the following three aspects:1.From the viewpoint of the Gibbs free energy and the size effect on interface energy,a thermodynamic model is established to determine the melting temperature of nanocrystals.The model indicated that,for isolated nanocrystals,the melting temperature decreases as the decrease of size and dimensionality.The variation in melting temperature is a synergy of breaking bonds and surface strain induced by the variation surface-to-volume ratio.The extent of depression in melting temperature relies on size and dimensionality.For nanoalloys of equal size and dimensionality,melting temperature decreases with increasing content of a lower surface energy.2.Considering the interface structure between nanocrystals and the matrix,a thermodynamic model is established to describe the interface effect on melting temperature.The model indicated that the necessary conditions for superheating could be summarized as the formation of a coherent or semi-coherent interface and the matrix with a higher melting temperature.3.Considering the relationship between Debye temperature and melting temperature,the established model has been extended to predict Debye temperature of nanocrystals.The Debye temperature of nanocrystals has the same tendency with the melting temperature as the variation in size,dimensionality,composition.The depression of the Debye temperature is the synergy of breaking bonds and surface strain.