(1. 江蘇大學(xué) 材料科學(xué)與工程學(xué)院, 鎮(zhèn)江 212013;
2. 中南大學(xué) 材料科學(xué)與工程學(xué)院, 長沙 410083)
摘 要: 利用緊束縛分子動力學(xué)的方法研究厚度為0.5～10.4 nm自由表面鉛納米薄膜的熔化溫度。 結(jié)果表明， 鉛納米薄膜的熔化溫度隨著薄膜厚度的減小而降低， 定量的數(shù)值結(jié)果與熱力學(xué)模型預(yù)測相一致。 薄膜厚度大于3個原子層時才有確定的熔化溫度， 而單原子層膜和雙原子層膜在熔化前就已經(jīng)破裂。 對于自由表面的納米薄膜， 薄膜的熔化從上下表面開始， 并逐漸向薄膜的中心逼近， 這不同于自由表面納米粒子的熔化過程， 即先表層熔化后內(nèi)部瞬間熔化。 薄膜的熔化開始溫度要低于熔化結(jié)束溫度， 這和相應(yīng)塊體材料的熔化溫度明顯不同。
關(guān)鍵字: 鉛納米薄膜； 熔化溫度； 尺寸效應(yīng)
（1. School of Materials Science and Engineering, Jiangsu University,
Zhenjiang 212013, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083 China）
Abstract: The tight-binding molecular dynamics method was used to study the size dependent melting temperature of Pd nanofilms with thickness of 0.5-10.4 nm. The results show that the melting temperature of Pb nanofilms decreases with decreasing the film thickness, and the simulated results are consistent with the predictions of thermodynamic model. The Pb films with more than 3 atomic layers have specified melting temperature, but not for these with less than 3 atomic layers. The melting of nanofilms starts from the surface and then approaches to the center of the films, which is different from those of nanoparticles with free surface (the surface shell melts first, and then the interior core melts instantaneous). Furthermore, the temperature of finishing melting is higher than that of beginning, which is different from those of the corresponding bulk materials.
Key words: Pb nanofilms; melting temperature; size effect
