materials

MX

-Cesium Chloride

-Rock Salt

-Nickel Arsenide

-Sphalerite

-Wurtzite

Cesium Chloride

SC lattice of anions, cubic holes filled with cations

ex:CsCl, CaS, TlCl, CsCN

[CN(M,X)=8)

Rock Salt

FCC lattice of anions X in which cations M occupy octahedral holes

 

ex: NaCl, LiCl, MgO, TiO, NiO, ScN

 

[CN(M,X)=6

Nickel Arsenide

HCP lattice of anions X, octahedral holes filled with M, X atoms surrounded in trigonal prismatic arrangement of M

 

ex: NiAs, NiS, FeS, CoS, CoTe

 

[CN(M,X)=6]

Sphalerite

 

FCC lattice of anions X in which cations M occupy tetrahedral holes

 

ex: ZnS, CuCl, CdS, HgS, GaP, InAs, CuFeS2

 

[CN(M,X)=4]

Wurtzite

HCP lattice of anions X in which cations M occupy tetrahedral holes

 

ex: ZnS, ZnO, BeO, AgI, SiC, InN, NH4F

 

[CN(M,X)=4]

MXand M2X

-fluorite

-antifluorite

Fluorite

FCC lattice of cations M in which anions X occupy tetrahedral holes

(CsCl structure in which on half of the cations are absent)

 

ex: CaF2, UO2, CeO2, BaCl2, HgF2, PbO2

 

[CN(M)=8, CN(X)=4]

Antifluorite

FCC lattice of anions X in which cations M occupy tetrahedral holes

(inverse of fluorite structure)

 

ex: M2O and M2S (M= Li, Na, K) 

 

[CN(M)=4, CN(X)=8]

ABX3
-perovskite
perovskite

cubic lattice with B (or A) at unit cell corners, X on edges, and A (or B) at the center

 

ex: CaTiO3, BaTiO3, SrTiO3, RbCaF3

 

[CN(A)=12, CN(B)=6]

Barkhausen Noise
due to pinning of domain walls by crystal defects
Hard Magnet

High resonance and large coercivity (> 100e)

 

-once polarized, will remain polarized=> useful as permanent magnetic material

Soft Magnet

Few defects and small coercivity (narrow loop, easily demagnetized)

 

=> usefule in electromagnets and transformer cores

MR= ?

Remanant magnetization 

 

(on the y axis of the hysterisis loop where the line crosses it)

 

magnetization oriented slightly more in one direction

HC= ?

Coercive field

 

(on the x axis where the curve meets it)

 

everything is exactly cancelled

Requirements for a single molecule magnet

1. High spin ground state, S=large

2. Axial zero-field splitting (D<0 => large -D is good)

3. Strong exchange coupling (|J|= large)

eq for x-ray diffraction
n(lamda) = 2dsin(theta)
crystalline

Long range (~10 nm) => will diffract x-rays

-molecular

-covalent

-ionic

-metallic

amorphous
will not diffract x-rays
cubic close packing (CCP)

(…ABCABCABC…)

CN=12

space filled= 74.05%

simple cubic (SC)

CN= 6

space filled= 52.36%

body centered cubic (BCC)

CN= 8

space filled = 68.02%

Hexagonal Closest Packing (HCP)

(…ABABABABAB…)

 

CN= 12

space filled= 74.05%

Van’t Hoff

?H ; 0

-endothermic

K2;K1

 

A(s) is deposited at cooler end (T1)

Van’t Hoff

?H< 0

-exothermic

K1>K2

 

A(s) is deposited at hotter end (T2)

Van’t Hoff Equation
ln(K2/K1) = (?H/R)((T2-T1)/T1T2)
n-type semiconductor

negative

adds electrons to LUMO

p-type semiconductor

think positive! 

 

empty HOMO 

Mechanisms for Interactions Between Magnetic Moments

1. Dipole-Dipole

2.Heisenburg Exchange

3. Super Exchange

4. Double Exchange

Dipole-Dipole

only worry about this at low temperatures

 

(between Metal-Metal bonds)

Heisenburg Exchange

weak when apart, strong when close

 

(direct Metal-Metal interactions)

 

J;0 exchange energy is minimum for parallel spins (ferromagnet)

J;0 exchange energy is minimum for antiparallel spins (antiferromagnet)

Super Exchange

exchange energy is dependent upon symmetry/overlap

exchange energy between metal-ligand bonds

 

(imagine p orbitals interacting with dx2-y2)

Double Exchange

paramagnet–> magnetic ordering below a certain temperature

 

-Tc= curie temp (ferri and ferro)

 

-TN= Neel temp (antiferro)

M-X ratio 0.225

tetrahedral

CN=4

ZnS

M-X ratio 0.414

octahedral

CN=6

 

NaCl

M-X ratio 0.732

cubic

CN=8

 

CsCl

M-X2 ratio 0.732

cubic

CN=8

Fluorite

 

CaF2 

 

M-X2 ratio 0.414

octahedral

CN=6

Rutile

 

TiO2

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