Periodic MP2, RPA, and Boundary Condition Assessment of Hydrogen Ordering in Ice XV
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- 作者：Mauro Del Ben ; Joost VandeVondele ; Ben Slater
- 刊名：The Journal of Physical Chemistry Letters
- 出版年：2014
- 出版时间：December 4, 2014
- 年：2014
- 卷：5
- 期：23
- 页码：4122-4128
- 全文大小：394K
- ISSN：1948-7185
文摘
Ice XV is the hydrogen-ordered form of the ice VI phase whose structure was predicted to be Cc and ferroelectric using periodic DFT approaches. However, neutron diffraction and Raman spectroscopy data show the structure to have P1虆 symmetry and to be antiferroelectric. Recent work1 using fragment-based MP2 and CCSD(T) approaches predicts the experimental structure as the ground state. We have reconsidered this problem using fully periodic MP2 and RPA approaches and find that the ferroelectric Cc structure is the lowest energy configuration. However, ubiquitously employed tinfoil boundary conditions stabilize polar structures. We suggest that ferroelectric Cc crystals can grow within a paraelectric ice VI matrix but may become unstable once a fraction of the matrix has become hydrogen-ordered. The reduction in dielectric constant causes P1虆 and other structures with small polarization to become favored, providing a possible resolution between observation and theoretical predictions.