By:ShaunPachecoHarveyMuddCollege

Advisor:Dr.PatrickSchellingUniversityofCentralFlorida

SilicateMinerals Compoundbearingsiliconanion  Foundinuppermantle(90%ofcrust)

 Olivine(Mg,Fe)2SiO4 Asteroids Weathersquickly

http://en.wikipedia.org/wiki/File:Peridot2.jpg

SiliconTetrahedron  3differentoxygensites

 O1furthestoxygen O2closestoxygen O3equidistant

O2

O3

O3

O1 Si

StructureofOlivineM2SiO4

 Orthorombic  ForsteriteMg2SiO4

  FayaliteFe2SiO4 Twometalsites  FeprefersM1siteM1

M1

M2

M2

Op8calProper8es DependentonMagnesium‐Ironconcentration

  Iron’svalenceelectronsleadstosmallerbandgap

Fayalite

http://en.wikipedia.org/wiki/File:Fayalite_crystal_group_‐_Ochtendung,_Eifel,_Germany.jpg

http://en.wikipedia.org/wiki/File:Forsterite_on_Sanidine_‐_Ochtendung,_Eifel,_Germany.jpg

Forsterite

DensityFunc8onalTheory Ground‐stateenergyuniquefunctionaloftheelectrondensity

  Findsetofwavefunctionsthatminimizeenergyfunctional.

!

"!2

2me

+Veff (" r )

#

$ %

&

' ( )* (" r ) = E*)* (

" r )

!

n! r ( ) = "#

$ ! r ( )"#

! r ( )

#

occ

%

PointDefects  SchottkyDefect–defectconsistingofananionandcationvacancyinfinitelyfarapart

  SchottkyDefectClusters–defectconsistingofananionandcationvacancy

http://en.wikipedia.org/wiki/File:Naclschottkydefect.svg

SpaceWeathering Createspointdefects Micrometeoriteimpacts  Solar‐windsputtering  Interactionswithcosmicrays

FiniteSizeEffects

SmallSystemMg1O3

LargerSystemMg1O3

M2

M2

M1

M2

M2 M1

SchoFkyDefectResults  Forsterite:

 Mg2‐O3defectlowestenergy3.65eV Mg2‐O2defecthighestenergy7.52eV

 Differentresultsthanempiricalpotentials

OxygenVacancy  Forsterite:O2sitemostenergeticallyfavorable8.45eV

  Fayalite:O3sitemostenergeticallyfavorable7.90eV

M1

M1

M2

M2

FutureWork Biggercellsizes  Furtherstudyopticalproperties Propertiesofolivineasfunctionofironcontent  Surfaces

Ques8ons?

References  Payne,etal.“Iterativeminimizationtechniquesforabinitiototal‐energycalculations:

moleculardynamicsandconjugategradients.”Oct1992.  http://en.wikipedia.org/wiki/File:Peridot2.jpg  http://en.wikipedia.org/wiki/File:Forsterite_on_Sanidine_‐

_Ochtendung,_Eifel,_Germany.jpg  http://en.wikipedia.org/wiki/File:Fayalite_crystal_group_‐

_Ochtendung,_Eifel,_Germany.jpg  http://en.wikipedia.org/wiki/File:Naclschottkydefect.svg