Advanced Centre of Research in High Energy Materials, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500 046, Andhra Pradesh, India.
J Chem Phys. 2013 May 7;138(17):174701. doi: 10.1063/1.4802722.
High pressure behavior of potassium chlorate (KClO3) has been investigated from 0 to 10 GPa by means of first principles density functional theory calculations. The calculated ground state parameters, transition pressure, and phonon frequencies using semiempirical dispersion correction scheme are in excellent agreement with experiment. It is found that KClO3 undergoes a pressure induced first order phase transition with an associated volume collapse of 6.4% from monoclinic (P2(1)/m) → rhombohedral (R3m) structure at 2.26 GPa, which is in good accord with experimental observation. However, the transition pressure was found to underestimate (0.11 GPa) and overestimate (3.57 GPa) using local density approximation and generalized gradient approximation functionals, respectively. Mechanical stability of both the phases is explained from the calculated single crystal elastic constants. In addition, the zone center phonon frequencies have been calculated using density functional perturbation theory at ambient as well as at high pressure and the lattice modes are found to soften under pressure between 0.6 and 1.2 GPa. The present study reveals that the observed structural phase transition leads to changes in the decomposition mechanism of KClO3 which corroborates with the experimental results.
采用第一性原理密度泛函理论计算研究了氯酸钾（KClO3）在 0 至 10 GPa 范围内的高压行为。用半经验色散校正方案计算得到的基态参数、转变压力和声子频率与实验结果非常吻合。研究发现，KClO3 在 2.26 GPa 时经历了由单斜（P2(1)/m）→三方（R3m）结构的一级压力诱导相变，伴随着 6.4%的体积收缩，这与实验观察结果一致。然而，用局域密度近似和广义梯度近似泛函分别计算得到的相变压力低估（0.11 GPa）和高估（3.57 GPa）。用计算得到的单晶弹性常数解释了两个相的力学稳定性。此外，在环境压力和高压下，使用密度泛函微扰理论计算了晶心声子频率，发现晶格模式在 0.6 至 1.2 GPa 之间的压力下软化。本研究表明，观察到的结构相变导致 KClO3 分解机制发生变化，这与实验结果相符。
