Pressure induced structural phase transition in solid oxidizer KClO3: A first-principles study

Abstract

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.

Structure and electronic properties of MNO3 (M: Li, Na, K, NH4) under pressure: DFT-D study

“…Since MNO 3 nitrates contain molecular complexes (nitrate anions, NH 4 cations), it is important to take into consideration the weak intermolecular Van der Waals interactions. DFT can predict the properties of the energetic materials that are in close agreement with experiments provided the exchange-correlation functionals are corrected to describe the weak intermolecular interactions [7,[42][43][44][45][46][47][48]. Thus, in comparison with to the LDA and GGA [49] results , G. Vaitheeswaran et al [7] found that the crystal structure of alkali-metal nitrates is well described by the dispersion-corrected functional DFT-D [50].…”

“…So, as regards transition pressure P tr , unfortunately, its adequate theoretical evaluation is impossible without calculation of vibrational structure. In contrast to KClO 3 [44], transition pressure for KNO 3 is relatively small [33,37]. Credibility of theoretical predictions of the pressure induced structural phase transitions using the pressure dependences of enthalpy H (P) = E + PV can be sufficiently high for the relatively high external pressure P >> 3kTN/(2V) [68], kthe Boltzmann constant, N-number of atoms.…”

“…Potassium chlorate (KClO 3 ) is another compound with molecular anion which has been investigated using semiempirical dispersion correction scheme Grimme [44,50]. It was found by N. Yedukondalu et al [44] that structural parameters and transition pressure are in excellent agreement with experiment. However, the transition pressure was found to underestimate and overestimate using local density approximation and generalized gradient approximation functionals, respectively.…”

“…Thus, in comparison with to the LDA and GGA [49] results , G. Vaitheeswaran et al [7] found that the crystal structure of alkali-metal nitrates is well described by the dispersion-corrected functional DFT-D [50]. Potassium chlorate (KClO 3 ) is another compound with molecular anion which has been investigated using semiempirical dispersion correction scheme Grimme [44,50]. It was found by N. Yedukondalu et al [44] that structural parameters and transition pressure are in excellent agreement with experiment.…”

Kinetic Study of the Thermal Decomposition of Potassium Chlorate Using the Non-isothermal TG/DSC Technique

“…Potassium perchlorate is, in turn, decomposed to yield potassium chloride and oxygen [12,13]. In the process of the thermal decomposition of KClO 3 , absorption of heat increases the diffusion speed and vibration amplitude of the crystals, causing cleavage and reformation of the Cl−O bonds in KClO 3 with subsequent formation of stable KClO 4 .…”