MgSiO_3后钙钛矿在三轴应力场中的第一原理模拟及地球物理学应用
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摘要
MgSiO3后钙钛矿具有明显的弹性各向异性,可以解释地球核幔边界D″层中地震波的不连续性等现象,但目前的研究对晶格优选方位的机理一直没有好的解释.针对复杂的D″层应力环境中晶体特性与应力场和晶轴取向的密切关联,引入三轴应力场对矿物性质进行约束,模拟应力场状态下后钙钛矿相弹性性质,通过最小能量原理获得稳定的晶体空间取向类型.对具有最小能量类型的晶体弹性常数和地震波速研究发现,晶体a轴取向平行于最大压缩方向;以b轴为垂直对称轴的剪切波横向各向异性(横向各向同性平均)大于静水力场中的剪切波横向各向异性.结果支持以(010)为主滑移面的观点,为D″层各向异性和晶体取向研究提供新的数据和证据.
MgSiO3 post-perovskite which is remarkably elastic anisotropic can explain the core-mantle boundary discontinuity(D″ discontinuity),but the mechanism for lattice preferred orientation still defies satisfactory explanation.Considering the complex stress environment of D″ and properties of minerals associated with the stress field and the orientation of crystallographic axes,single-crystal energy in triaxial stress field was calculated to study elastic constants,single crystal and aggregated acoustic velocities.The conditions were found under which energy is a minimum.The calculation results show that the a-axes tend to align paralleling to the maximal compression direction,and transversely anisotropism in shear wave velocities with the b-axis as vertical symmetry axis becomes greater than that under the condition in hydrostatic stress field.The results also support(010) plane as the dominant slip plane and do supply new evidence of LPO and anisotropic properties of D″ layer.
MgSiO3 post-perovskite which is remarkably elastic anisotropic can explain the core-mantle boundary discontinuity(D″ discontinuity),but the mechanism for lattice preferred orientation still defies satisfactory explanation.Considering the complex stress environment of D″ and properties of minerals associated with the stress field and the orientation of crystallographic axes,single-crystal energy in triaxial stress field was calculated to study elastic constants,single crystal and aggregated acoustic velocities.The conditions were found under which energy is a minimum.The calculation results show that the a-axes tend to align paralleling to the maximal compression direction,and transversely anisotropism in shear wave velocities with the b-axis as vertical symmetry axis becomes greater than that under the condition in hydrostatic stress field.The results also support(010) plane as the dominant slip plane and do supply new evidence of LPO and anisotropic properties of D″ layer.
引文
[1]Oganov A R,Ono S.Theoretical and experimentalevidence for a post-perovskite phase of MgSiO3inEarth s D″layer[J].Nature,2004,430:445-448.
[2]Murakami M,Hirose K,Kawamura K,et al.Post-perovskite phase transition in MgSiO3[J].Science,2004,304:855-858.
[3]Mao W L,Shen G,Prakapenka V B,et al.Ferromagnesian post-perovskite silicates in the D″layerof the Earth[J].Proc Nat Acad Sci USA,2004,101:15 867-15 869.
[4]Shim S-H,Duffy T S,Jeanloz R,et al.Stability andcrystal structure of MgSiO3perovskite to the core-mantle boundary[J].Geophys Res Lett,2004,31.L10603.
[5]Caracas R,Cohen R E.Effect of chemistry on thestability and elasticity of the perovskite and post-perovskite phases in the MgSiO3-FeSiO3-Al2O3systemand implications for the lowermost mantle[J].Geophys Res Lett,2005,32.L16310.
[6]Hernlund J W,Thomas C,Tackley P J.A doubling ofthe post-perovskite phase boundary and structure of theEarth s lowermost mantle[J].Nature,2005,434:882-886.
[7]Murakami M,Hirose K,Sata N,et al.Post-perovskite phase transition and mineral chemistry in thepyrolitic lowermost mantle[J].Geophys Res Lett,2005,32.L03304.
[8]Tsuchiya T,Tsuchiya J,Umemoto K,et al.Phasetransition in MgSiO3perovskite in the Earth s lowermantle[J].Earth Planet Sci Lett,2004,224:241-248.
[9]Lay T,Helmberger D V.A shear velocitydiscontinuity in the lower mantle[J].Geophys ResLett,1983,10:63-66.
[10]Lay T,Williams Q,Garnero E J.The core-mantleboundary layer and deep Earth dynamics[J].Nature,1998,392:461-468.
[11]Panning M,Romanowicz B.Inferences on flow at thebase of Earth s mantle based on seismic anisotropy[J].Science,2004,303:351-353.
[12]Iitaka T,Hirose K,Kawamura K,et al.The elasticityof the MgSiO3post-perovskite phase in the Earth slowermost mantle[J].Nature,2004,430:442-445.
[13]Tsuchiya T,Tsuchiya J,Umemoto K,et al.Elasticityof post-perovskite MgSiO3[J].Geophys Res Lett,2004,31.L14603.
[14]Wentzcovitch R A,Tsuchiya T,Tsuchiya J.MgSiO3post-perovskite at D″conditions[J].Proc Nat AcadSci USA,2006,103:543-546.
[15]Oganov A R,Martonak R,Laio A,et al.Anisotropyof Earth s D″layer and stacking faults in the MgSiO3post-perovskite phase[J].Nature,2005,438:1 142-1 144.
[16]Kresse G,Furthmüller J.Efficiency of ab initio total-energy calculations for metals and semiconductors usinga plane-wave basis set[J].Comp Mater Sci,1996,6:15-50.
[17]Bl chl P E.Projector augmented-wave method[J].Phys Rev B,1994,50:17 953-17 979.
[18]Kresse G,Joubert D.From ultrasoft pseudopotentialsto the projector augmented-wave method[J].PhysRev B,59,1999:1 758-1 775.
[19]Perdew J P,Burke K,Ernzerhof M.Generalizedgradient approximation made simple[J].Phys RevLett,1996,77:3 865-3 868.
[20]Monkhorst H J,Pack J D.Special points for Brillouin-zone integrations[J].Phys Rev B,1976,13:5 188-5 192.
[21]Karki B B,Stixrude L,Clark S J,et al.Structure andelasticity of MgO at high pressure[J].Am Mineral,1997,82:52-61.
[22]Oganov A R,Brodholt J P,Price G D.Ab initioelasticity and thermal equation of state of MgSiO3Perovskite[J].Earth Planet Sci Lett,2001,184:555-560.
[23]Karki B B,Stixrude L,Clark S J,et al.Elasticproperties of orthorhombic MgSiO3perovskite at lowermantle pressures[J].Am Mineral,1997,82:635-638.
[24]Ross N L,Hazen R M.Single crystal X-ray diffractionstudy of MgSiO3perovskite from 77 to 400 K[J].PhysChem Miner,1989,16:415-420.
[25]Yeganeh-Haeri A.Synthesis and re-investigation of theelastic properties of single-crystal magnesium silicateperovskite[J].Phys Earth Planet Inter,1994,87:111-121.
[26]Musgrave M J P.Crystal Acoustics[M].SanFrancisco:Holden-Day,1970:288.
[27]Montagner J P,Nataf H C.A simple method forinverting the azimuthal anisotropy of surface waves[J].J Geophys Res,1986,91:511-520.
[28]Love A E H.A Treatise on the Mathematical Theoryof Elasticity[M].4th ed.Cambridge:CambridgeUniversity Press,1927:1-643.
[29]Merkel S,Kubo A,Miyagi L,et al.Plasticdeformation of MgGeO3post-perovskite at lowermantle pressures[J].Science,2006,311:644-646.
[30]Karato Shun-ichiro.Some remarks on the origin ofseismic anisotropy in the D″layer[J].Earth PlanetsSpace,1998,50:1 019-1 028.
[2]Murakami M,Hirose K,Kawamura K,et al.Post-perovskite phase transition in MgSiO3[J].Science,2004,304:855-858.
[3]Mao W L,Shen G,Prakapenka V B,et al.Ferromagnesian post-perovskite silicates in the D″layerof the Earth[J].Proc Nat Acad Sci USA,2004,101:15 867-15 869.
[4]Shim S-H,Duffy T S,Jeanloz R,et al.Stability andcrystal structure of MgSiO3perovskite to the core-mantle boundary[J].Geophys Res Lett,2004,31.L10603.
[5]Caracas R,Cohen R E.Effect of chemistry on thestability and elasticity of the perovskite and post-perovskite phases in the MgSiO3-FeSiO3-Al2O3systemand implications for the lowermost mantle[J].Geophys Res Lett,2005,32.L16310.
[6]Hernlund J W,Thomas C,Tackley P J.A doubling ofthe post-perovskite phase boundary and structure of theEarth s lowermost mantle[J].Nature,2005,434:882-886.
[7]Murakami M,Hirose K,Sata N,et al.Post-perovskite phase transition and mineral chemistry in thepyrolitic lowermost mantle[J].Geophys Res Lett,2005,32.L03304.
[8]Tsuchiya T,Tsuchiya J,Umemoto K,et al.Phasetransition in MgSiO3perovskite in the Earth s lowermantle[J].Earth Planet Sci Lett,2004,224:241-248.
[9]Lay T,Helmberger D V.A shear velocitydiscontinuity in the lower mantle[J].Geophys ResLett,1983,10:63-66.
[10]Lay T,Williams Q,Garnero E J.The core-mantleboundary layer and deep Earth dynamics[J].Nature,1998,392:461-468.
[11]Panning M,Romanowicz B.Inferences on flow at thebase of Earth s mantle based on seismic anisotropy[J].Science,2004,303:351-353.
[12]Iitaka T,Hirose K,Kawamura K,et al.The elasticityof the MgSiO3post-perovskite phase in the Earth slowermost mantle[J].Nature,2004,430:442-445.
[13]Tsuchiya T,Tsuchiya J,Umemoto K,et al.Elasticityof post-perovskite MgSiO3[J].Geophys Res Lett,2004,31.L14603.
[14]Wentzcovitch R A,Tsuchiya T,Tsuchiya J.MgSiO3post-perovskite at D″conditions[J].Proc Nat AcadSci USA,2006,103:543-546.
[15]Oganov A R,Martonak R,Laio A,et al.Anisotropyof Earth s D″layer and stacking faults in the MgSiO3post-perovskite phase[J].Nature,2005,438:1 142-1 144.
[16]Kresse G,Furthmüller J.Efficiency of ab initio total-energy calculations for metals and semiconductors usinga plane-wave basis set[J].Comp Mater Sci,1996,6:15-50.
[17]Bl chl P E.Projector augmented-wave method[J].Phys Rev B,1994,50:17 953-17 979.
[18]Kresse G,Joubert D.From ultrasoft pseudopotentialsto the projector augmented-wave method[J].PhysRev B,59,1999:1 758-1 775.
[19]Perdew J P,Burke K,Ernzerhof M.Generalizedgradient approximation made simple[J].Phys RevLett,1996,77:3 865-3 868.
[20]Monkhorst H J,Pack J D.Special points for Brillouin-zone integrations[J].Phys Rev B,1976,13:5 188-5 192.
[21]Karki B B,Stixrude L,Clark S J,et al.Structure andelasticity of MgO at high pressure[J].Am Mineral,1997,82:52-61.
[22]Oganov A R,Brodholt J P,Price G D.Ab initioelasticity and thermal equation of state of MgSiO3Perovskite[J].Earth Planet Sci Lett,2001,184:555-560.
[23]Karki B B,Stixrude L,Clark S J,et al.Elasticproperties of orthorhombic MgSiO3perovskite at lowermantle pressures[J].Am Mineral,1997,82:635-638.
[24]Ross N L,Hazen R M.Single crystal X-ray diffractionstudy of MgSiO3perovskite from 77 to 400 K[J].PhysChem Miner,1989,16:415-420.
[25]Yeganeh-Haeri A.Synthesis and re-investigation of theelastic properties of single-crystal magnesium silicateperovskite[J].Phys Earth Planet Inter,1994,87:111-121.
[26]Musgrave M J P.Crystal Acoustics[M].SanFrancisco:Holden-Day,1970:288.
[27]Montagner J P,Nataf H C.A simple method forinverting the azimuthal anisotropy of surface waves[J].J Geophys Res,1986,91:511-520.
[28]Love A E H.A Treatise on the Mathematical Theoryof Elasticity[M].4th ed.Cambridge:CambridgeUniversity Press,1927:1-643.
[29]Merkel S,Kubo A,Miyagi L,et al.Plasticdeformation of MgGeO3post-perovskite at lowermantle pressures[J].Science,2006,311:644-646.
[30]Karato Shun-ichiro.Some remarks on the origin ofseismic anisotropy in the D″layer[J].Earth PlanetsSpace,1998,50:1 019-1 028.
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