Ti3O5弹性、电子和光学性质的第一性原理研究

First-principles investigation on elastic, electronic, and optical properties of Ti3O5

采用基于密度泛函理论的第一性原理方法计算了λ和β相Ti3O5的电子结构、弹性性质和光学性质.这两相间的相变可以被光、热、压力、电流等多种方式驱动,在光学存储以及热能存储领域都有广泛的应用前景.本文报道了这两相一系列的弹性常数.计算发现,两相间的光吸收及光反射性质具有很大差异.同时提出了两相间的光致相变机制是由受激辐射效应决定的构想.

Ti3O5 is a highly anticipated functional material due to its intriguing physical properties and multiincentive phase transition process.This material undergoes a reversible first-order phase transition between λphase and β phase,accompanied by drastic changes in the electronic and atomic structure.The amazing way of changing phase such as light,heat,pressure and electric current makes this material promise to be used in future optical information storage and heat storage.In this work,structural,elastic,electronic and optical properties of λ-Ti3O5 and β-Ti3O5 are calculated by using a first-principles approach,according to density functional theory(DFT).The LSDA,GGA-PBE,GGA-91,GGA-PS and GGA-RP are compared among them to obtain a suitable method of characterizing the crystal structure and electronic structure of λ-Ti3O5 and β-Ti3O5.The energy gap at the Fermi level of β-Ti3O5 can be obtained only when the extra Coulomb correlation U effect of Ti3 d electrons is considered.A complete set of elastic parameters for both phases are first reported.The calculated elastic constant satisfies the Born stability criterion,indicating that λ phase and β phase have good mechanical structural stability.The two phases are more resistant to volume changes than to shape changes and both behave as ductile materials.On the(010)plane,the elastic anisotropy of λ phase is weaker than that of β phase.Studies on the electronic structure show that the local charge of Ti3 is transferred to Ti2,resulting in the transformation of the semiconductor β phase to the metal λ phase.There are large differences in optical property such as absorption and reflectivity between these two structures,indicating that they can be applied to the field of optical storage materials.In this paper we also present a new insight into the photoinduced phase transition process of this material.The mechanism of photoinduced phase transition fromλ-Ti3O5 to β-Ti3O5 is considered as stimulated emission effect.The results are of significance particularly for practically applying Ti3O5and understanding its phase change mechanism.