Rici Yu

First-Principles Determination of Chain-Structure Instability in KNbO3.

A complete mapping in the Brillouin zone of the structural instability associated with the ferroelectric phase transitions of KNbO

Ab initio linear response study of SrTiO3

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POLARIZATION DEPENDENCE OF BORN EFFECTIVE CHARGE AND DIELECTRIC CONSTANT IN KNBO3

has been obtained by first-principles calculations using an LAPW linear response approach. The wavevector dependence of the instability reveals pronounced two-dimensional character, which corresponds to chains oriented along

Dynamic local distortions in KNbO3

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Pressure dependence of Born effective charges, dielectric constant, and lattice dynamics in SiC.

\ directions of displaced Nb atoms. The results are discussed in relation to models of the ferroelectric phase transitions.

Precursor structures in ferroelectrics from first-principles calculations

Abstract The lattice instabilities of perovskite structure oxides are responsible for many of their interesting properties, such as temperature-dependent ferroelectric phase transitions. First-principles calculations using linear response theory provide an accurate means to determine the lattice dynamics throughout the entire Brillouin zone (BZ). Using the LAPW linear response method[1], we have previously carried out such a study on ferroelectric KNbO3 [2]. We present here the results of a similar investigation for cubic SrTiO3. While KNbO3 has only ferroelectric-type instabilities, SrTiO3 exhibits both ferroelectric (FE) and antiferrodistortive (AFD) instabilities. We correctly predict the known instability at the R-point in the Brillouin zone, which is responsible for the AFD phase transition to the tetragonal structure at about 105 K. Furthermore, the phase space of the ferroelectric instability is greatly reduced compared to KNbO3. Antiferrodistortive instabilities exist in one-dimensional cylindrica...

Born effective charges, dielectric constants, and lattice dynamics of KNbO3

The Born effective charge

Wavevector dependence of ferroelectric instabilities in KNbO3

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Lattice dynamics of ferroelectrics using the lapw linear response method: Application to KNbO3

and dielectric tensor

Linear response calculations using lapw and mixed basis methods

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