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The δ-AIOOH can transport water into the deep mantle along cold subducting slab geothenn. We investigate the hydrogen-bond symmetrization behavior of δ-AIOOH under the relevant pressure-temperature condition of the lower mantle using ab initio molecular dynamics(AID). The static symmetrization pressure of 30.0 GPa can be reduced to 17.0 GPa at 300 K by finite-temperature(T) statistics, closer to the experimental observation of-10.0 GPa. The symmetrization pressure obtained by MD simulation is related to T by P(GPa) = 13.9(GPa) +0.01(GPa/K) × T(K). We conclude that δ-AIOOH in the lower mantle exists with symmetric hydrogen bond from its birthplace, or someplace slightly deeper, to the core-mantle boundary(CATB) along cold subducting slab geotherm. The bulk modulus decreases with T and increases anomalously upon symmetrization: K_o(GPa) =181(GPa)-0.013(GPa/K) × T(K) for δ-AIOOH with asymmetric hydrogen bond, and K_o(GPa) = 216(GPa)-0.013(GPa/K) × T(K) for δ-AIOOH with symmetric hydrogen bond. Our results provide an important insight into the existent form and properties of δ-AIOOH in the lower mantle.
The δ-AIOOH can transport water into the deep mantle along cold subducting slab geothenn. We investigate the hydrogen-bond symmetrization behavior of δ-AIOOH under the relevant pressure-temperature condition of the lower mantle using ab initio molecular dynamics (AID). The The symmetrization pressure obtained by MD simulation is related to T by P (GPa). The static symmetrization pressure of 30.0 GPa can be reduced to 17.0 GPa at 300 K by finite-temperature (T) statistics, closer to the experimental observation of-10.0 GPa. = 13.9 (GPa) +0.01 (GPa / K) × T (K). We conclude that δ-AIOOH in the lower mantle exists with either symmetric hydrogen bond from its birthplace, or someplace slightly deeper, to the core- mantle boundary (CATB The bulk modulus decreases with T and increases anomalously upon symmetrization: K_o (GPa) = 181 (GPa) -0.013 (GPa / K) × T (K) for δ-AIOOH with asymmetric hydrogen bond, and K_o (GPa) = 216 (GPa) -0.013 (GPa / K) × T (K) for δ-AIOOH with symmetric h ydrogen bond. Our results provide an important insight into the existent form and properties of δ-AIOOH in the lower mantle.