First-principles study on dielectric properties of NaCl crystal and   ultrathin NaCl films under finite external electric field
  We present a first-principles study on the dielectric properties of an NaCl crystal and ultrathin NaCl films under a finite external electric field. Our results show that the high-frequency dielectric constant of the films is not affected by the finite size effect from crystal surfaces and is close to that of the crystal, whereas the static one is sensitive to the thickness of the film due to the difference in the atomic configurations between the surface and inside of the film. 
Tomoya Ono and Kikuji Hirose