5 research outputs found
First-principles study of stability and vibrational properties of tetragonal PbTiO_3
A first-principles study of the vibrational modes of PbTiO_3 in the
ferroelectric tetragonal phase has been performed at all the main symmetry
points of the Brillouin zone (BZ). The calculations use the local-density
approximation and ultrasoft pseudopotentials with a plane-wave basis, and
reproduce well the available experimental information on the modes at the Gamma
point, including the LO-TO splittings. The work was motivated in part by a
previously reported transition to an orthorhombic phase at low temperatures
[(J. Kobayashi, Y. Uesu, and Y. Sakemi, Phys. Rev. B {\bf 28}, 3866 (1983)]. We
show that a linear coupling of orthorhombic strain to one of the modes at Gamma
plays a role in the discussion of the possibility of this phase transition.
However, no mechanical instabilities (soft modes) are found, either at Gamma or
at any of the other high-symmetry points of the BZ.Comment: 8 pages, two-column style with 3 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#ag_pbt
Should science educators deal with the science/religion issue?
I begin by examining the natures of science and religion before looking at the ways in which they relate to one another. I then look at a number of case studies that centre on the relationships between science and religion, including attempts to find mechanisms for divine action in quantum theory and chaos theory, creationism, genetic engineering and the writings of Richard Dawkins. Finally, I consider some of the pedagogical issues that would need to be considered if the science/religion issue is to be addressed in the classroom. I conclude that there are increasing arguments in favour of science educators teaching about the science/religion issue. The principal reason for this is to help students better to learn science. However, such teaching makes greater demands on science educators than has generally been the case. Certain of these demands are identified and some specific suggestions are made as to how a science educator might deal with the science/religion issue. © 2008 Taylor & Francis