中文摘要：

采用基于密度泛函理论（DFT）的平面波超软赝势法，用广义梯度近似（GGA）PBE交换相关泛函，对P42／mnm和Pnnm晶体结构SnO2的力学性质进行第一性原理计算。计算表明，两种结构SnO2的晶体结构参数与实验和理论值符合较好。随着压强的增大，P42／mnm型SnO2的生成焓呈抛物线状缓慢增大，Pnnm型Sn0。的生成焓为一直线迅速上升。P42／mnm结构弹性常数随压强增加规律增大，Pnnm结构弹性常数无规律性变化，外界压强为11．06GPa时发生相变。两结构中低指数面中Pnnm结构的{100}晶面族之间滑移的可能性最大、最不稳定，{001）晶面族间结合最牢固。金红石型snO。维氏硬度计算理论值为10．49GPa，Pnnm结构为11．42GPa。德拜温度计算表明，结构对称性高低的差异，造成P42／mnm结构德拜温度在一个小范围内波动，而Pnnm结构德拜温度在8～10GPa内有突变，呈缓慢下降的趋势。

英文摘要：

In the present work we performed the first principles calculations based on the density functional theory and investigated the P42/mnm--Pnnm phase transition and the mechanical properties of SnO2. For the exchange-correction energy we employed the generalized gradient approximation （GGA） in the Perdew,Burke and Ernzerhof （PBE） form. The elastic stiffness coefficients, co, bulk modulus, shear modulus,Young modulus, Reuss modulus,Voigt modulus and anisotropy factor were calculated for two polymorphs of SnO2 ：rutile and CaCl2 structure. Our results for the structural parameters and elastic constants at the equilibrium phase are in good agreement with the available theoretical and experimental values. Using the enthalpy-pressure data, we observed the rutile to CaCl2 structural phase transition under 11.06 OPa pressure. In the low index plane of two polymorphs＇ SnO2, the most unstable and the possibility of slippage crystal planes was the { 100} crystal planes of Pnnrn structure, and the {001} crystal planes has the strongest binding force. The Viekers hardness calculated for the P42/rnnrn of SnO2 was 10.49 GPa,and the Pnnm structure was 11.42 GPa. Because of the differences in the level of the structure symmetry, results from calculation show that the Debye temperature waverd in a small range for the utile structure but it had mutations in 8-10 GPa and showed a downward trend for the CaCl2 structure.