http://www.sciencemag.org/cgi/content/full/319/5864/797?rss=1
 http://www.sciencemag.org/cgi/content/full/319/5864/797?rss=1

Science 8 February 2008:
Vol. 319. no. 5864, pp. 797 - 800
DOI: 10.1126/science.1150302
Elastic Anisotropy of Earth\'s Inner Core

Earth\'s solid-iron inner core is elastically anisotropic. Sound waves propagate faster along Earth\'s spin axis than in the equatorial plane. This anisotropy has previously been explained by a preferred orientation of the iron alloy hexagonal crystals. However, hexagonal iron becomes increasingly isotropic on increasing temperature at pressures of the inner core and is therefore unlikely to cause the anisotropy. An alternative explanation, supported by diamond anvil cell experiments, is that iron adopts a body-centered cubic form in the inner core. We show, by molecular dynamics simulations, that the body-centered cubic iron phase is extremely anisotropic to sound waves despite its high symmetry. Direct simulations of seismic wave propagation reveal an anisotropy of 12%, a value adequate to explain the anisotropy of the inner core.

전에는 지구 핵속의 Fe 가 hexagonal phase 인 걸로 사람들이 생각했는데, 지들이 계산해 보니 BCC (Body Centered Cubic) Fe 라는 얘기인 듯. <i>P</i> = 360.0 GPa 에서 <i>T</i> = 6600 K 조건에서 BCC Fe 라고 하고 계산하니 잘 들어맞는다고 함.

아래 기사의 지구핵이 주사위 모양으로 생겼다는건 결정구조론을 안 들은 기자의 무지함 탓.

울나라 기자들 흠좀무.