线度和非简谐效应对Ag纳米晶热力学性质的影响

Influences of Size and Anharmonic Effect on Thermodynamic Properties of Ag Nano-crystalline

应用固体物理和统计物理的理论,考虑原子作非简谐振动,从微观角度研究了Ag纳米晶的热膨胀系数、格林乃森常数、化学势等随温度的变化规律.结果表明:①在简谐近似下,Ag纳米晶不会有热膨胀,其格林乃森常数为零,非简谐效应导致热膨胀系数和格林乃森常数都随着温度升高而增大,但变化较慢.②球形Ag纳米晶的化学势大于平面块状晶体的化学势,且粒子线度愈小,两者相差愈大;其中,由界面弯曲引起的化学势修正μ′e随粒径的减小而增大,粒径较大时,μe′将不变.③球形Ag纳米晶受温度的影响大于平面块状晶体,总化学势随温度升高而减小,但变化缓慢,由界面弯曲引起的化学势修正μ′e随温度升高而增大,且温度愈高,μ′e的变化速度愈快.④非简谐效应影响纳米晶热力学性质的本质在于它改变了原子的相互作用势形式和总相互作用能.

Applying theory of solid state physics and statistical physics,considering anharmonic vibration of atoms,from microscopic angle,the change law of thermal expansion coefficient,Grüneisen constant and chemical potential of Ag nano-crystalline with temperature is studied： ①In simple harmonic approximation,there will be no thermal expansion in nanocrystalline,Grüneisen constant is zero,Unharmonic effect causes the thermal expansion coefficient and Grüneisen constant to increase with temperature,but change slowly.②Chemical potential of spherical nanoparticles is larger than plane and block.And the smaller the particle＇s size,the larger their gap.Thereinto,the correction of chemical potential due to bending interface,μ′e,decreases with particle size.When the particle size is larger,μ′e keeps invariant.③Spherical nanoparticle is effected more by temperature than block.The total chemical potential decreased with temperature,but changes slowly.The correction of chemical potential due to bending interface increases with temperature,and the higher the temperature,the faster it changes.④The essence of influence for Unharmonic effect on the thermodynamic properties of nanocrystalline is that it changes the type of atomic interaction potential and total interaction energy.