Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (8): 1432-1436.doi: 10.3866/PKU.WHXB201405281

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Effects of A-Site Substitutions on Negative Thermal Expansion in PbTiO3 fromFirst-Principles Calculations

WANG Fang-Fang1, CAO Zhan-Min2, CHEN Jun1, XING Xian-Ran1   

  1. 1. Department of Physical Chemistry, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China;
    2. Department of Nonferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
  • Received:2014-03-17 Revised:2014-05-28 Published:2014-07-18
  • Contact: XING Xian-Ran E-mail:xing@ustb.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21231001, 21031005, 21322102).

Abstract:

Recent experimental results have indicated that the negative thermal expansion is a common phenomenon in PbTiO3-based materials, and that this expansion is affected by various substitutions. Interestingly, Cd substitution in PbTiO3 has a unique effect compared with other A-site substitutions, in that it enhances negative thermal expansion. Therefore, studying A-site substitution in PbTiO3, the role of which still remains unclear, would provide a deeper understanding of the nature of the negative thermal expansion of PbTiO3-based materials. Herein we report the results of structural calculations, densities of states and the minimumelectron densities of Pb1-xSrxTiO3, Pb1-xBaxTiO3, and Pb1-xCdxTiO3 supercells on the basis of chemical bond first-principles calculations. The results demonstrate that the hybridization between Cd―O orbitals is more pronounced than that between Pb―O orbitals, while the bonding between Ba/Sr and O is almost ionic in nature. Cd substitution was found to have an unusual effect in terms of enhancing the average bulk coefficient of thermal expansion in PbTiO3. In contrast, Ba and Sr substitutions reduce the coefficient. Thus, the covalency in the bonding between the A- site and O in PbTiO3- based materials is responsible for the enhanced negative thermal expansion.

Key words: Density function theory, Negative thermal expansion, PbTiO3, Density of states, Structure calculation

MSC2000: 

  • O641