金属Mo和W纳米晶表面能及形成焓的计算.pdf

The calculation of surface energies and formation enthalpies of metallic Mo and W nanocrystals D. Xie *, M. P. Wang, L. F. Cao, Y. L. Jia School of Materials Science and Engineering, Central South University, Changsha 410083, China * Author to whom correspondence should be addressed. Tel.: +86-731-8830264. Fax: +86-731-8876692. E-mail: patriot_csu@163.com Abstract A simple but valid equation for the higher surface energies of metallic nanocrystals is obtained, the formation enthalpies of nanocrystals are calculated by using the equation of surface energies, and the structure variation induced formation enthalpies are also discussed. The calculated surface energy values of Ag and Au nanocrystals are in excellent agreement with the corresponding newest experimental values, and the predicted formation enthalpy values are consonant with the corresponding experimental values of Mo and W nanocrystals. Keywords：Metallic nanocrystals, Surface energy, Formation enthalpy Since Kim et al. [1] reported the first experimental data on the formation enthalpies of Mo and W by measuring the oxidation enthalpies of nanocrystals, several authors began to investigate the important thermodynamic parameter theoretically [2-4]. Despite the success, most of the models established in the literatures under different theoretical origins, avoided to discuss the structure variations of nanocrystals which could directly influence the formation enthalpies ( for example, the structure of Mo and W nanocrystals can be changed from BCC structure to FCC structure with crystals size decreasing [1] ), and can not determine the surface induced and structural 1 induced fo