球形金属纳米颗粒熔化温度、熔化熵及熔化焓的尺寸效应

Size-dependent melting temperature,melting entropy and melting enthalpy of metallic nanoparticles with ball shape

根据结合能的键能模型,研究了球形金属纳米颗粒熔化相关热力学量的尺寸效应.在该模型中引入3个因子:晶体致密度k因子(晶胞中原子总体积与晶胞体积的比值);β因子(晶体中表面原子与内部原子结合能的比值)和qs因子(晶面被表面原子占据的比值).在考虑上述因子后,通过模型预测具有自由表面球形金属纳米颗粒的熔化温度、熔解熵、熔解焓等热力学量的尺寸依赖性,并将所得结果与相关实验数据、分子动力学模拟结果、液滴模型以及前人提出的模型进行了比较.结果显示,对于Au和Al纳米粒子熔化温度的尺寸效应,该模型相比之前的模型更接近实验结果,与Ag和Cu纳米粒子熔化熵与熔化焓的分子动力学结果吻合较好.

Size-dependent melting thermodynamic quantities of metallic nanoparticles with ball shape are studied theoretically based on bond energy model.Three factors are introduced in the present model. The k factor,i.e.,efficiency of space filling of crystal lattice （the ratio between the volume of the atoms in a crystal cell and that of the crystal cell）.Theβfactor （the ratio between the cohesive energy of sur-face atom and interior atom of a crystal）.The qs factor （the packing fraction on a surface crystalline plane）.With considering these factors,the melting temerature,melting entropy and melting enthalpy of free standing metallic nahoparticles with ball shape are predicated by the present model.The obtained model is also compared with the reported experimental data ,molecular dynamics simulation results and the liquid drop model and the model by Qi.For the size effect on melting temperature of Au and Al nan-oparticles,the results show that the present model is more close to the experimental data compared with the model by Qi.Compared with the molecular dynamics simulation results,it is show that such model can successfully predict the size-dependent melting entropy and enthalpy curves of Ag and Cu nanoparti-cles.