An unusual structural phase transition in Rb2HfF6

An unusual structural phase transition in the crystalline compound Rb2HfF6 near room temperature has been observed from perturbed angular correlation (PAC) spectroscopy. Our measurements in this compound produce two different crystalline configurations characterized by ωQ=74.1(1) Mrad/s, η~0, δ~0 and ωQ=24.7(2) Mrad/s, η=0.53(1), and δ=4(2)%. From PAC measurements in different samples, it is found that crystal structure corresponding to ωQ=74 Mrad/s, η~0 transforms to the other quite arbitrarily with temperature and no definite temperature corresponding to this transition has been observed. This can possibly be attributed to displacive phase transition.