Term
| What are the hkl conditions for different lattice types for diffraction |
|
Definition
P cubic- none
I - h+k+l = 2n
C - h+k = 2n
F h,k,l all odd or all even |
|
|
Term
| What are the characteristics (lattice parameter restrictions, angle restriction, characteristic symmetry) of the seven crystal systems? |
|
Definition
Triclinic a1 not= a2 not= a3; alpha not= beta not= gamma; monad symmetry
monoclinic a1 not = a2 not= a3; alpha = gamma beta>= 90; 1 diad
orthorhombic a1 not= a2 not=a3; alpha= beta= gamma = 90; 3 diads
tetragonal a1 = a2 not= a3; alpha= beta= gamma = 90; 1 tetrad
trigonal a1 = a2 = a3; alpha = beta = gamma not= 90; 1 triad
hexagonal a1 = a2 not= a3; alpha = beta = 90 gamma = 120; 1 hexad
cubic a1=a2=a3; alpha= beta= gamma= 90;; 4 triads |
|
|
Term
| What are the 14 bravais lattices? |
|
Definition
| Triclinic P; Monoclinic P&C; Orthorhombic P,C, I&F; Tetragonal P&I, Hexagonal, Trigonal P; Cubic P,F &I |
|
|
Term
| What are the 14 bravais lattices? |
|
Definition
| Triclinic P; Monoclinic P&C; Orthorhombic P,C, I&F; Tetragonal P&I, Hexagonal, Trigonal P; Cubic P,F &I |
|
|
Term
| What is Weiss zone rule? How do you prove it? |
|
Definition
If a direction [uvw] is contained in a plane (hkl) then the normal to the plane is perpendicular to the direction:
(ha*+kb*+lc*)(ua+vb+wc) = 0
a*a = 1, b*b = 1, c*c=1
hu + kv+ lw = 0 (weiss zone rule) |
|
|
Term
| Which Bravais lattices have a centre of symmetry? |
|
Definition
|
|
Term
|
Definition
| the collection of symmetry operations passing through a point. |
|
|
Term
| What does m represent? What do bars on top of rotation axes represent? 2/m? mm2? how else can you write mm2? What does the first number represent? What's the exception to the rule stated earlier |
|
Definition
| m - mirror; bars- inversion axes; 2/m- mirror plane perpendicular to a diad axes; mm2- two mirror planes intersecting at a two-fold axis- can also be written as mm or 2m; the first number always refers to a c-axis except in the monoclinic system where the b axis is unique. |
|
|
Term
| In a cubic crystal/stereogram, which planes have triad symmetry? tetrad symmetry? diad symmtery? |
|
Definition
triad- {111}
tetrad- {100}
diad- {100} and {110} |
|
|
Term
| What is the requirement for a crystal to be piezoelectric? |
|
Definition
| Must lack a centre of symmetry |
|
|
Term
| What are polar point groups? |
|
Definition
| point groups that have a unique direction which is not related by the symmetry elements to any other |
|
|
Term
| In the hkil notation used for hexagonal crystal systems, what is the relationship between i and h, k, and l? |
|
Definition
|
|
Term
| What is a diagonal glide plane and what is its symbol? |
|
Definition
| the translations involve two orthogonal steps parallel to a face of the unit cell. It's symbol is n. |
|
|
Term
| What are the different types of glides? there symbols and characteristics? |
|
Definition
An axial glide is parallel to one of the lattice vectors and has the symbol of the axis it's parallel to.
A diagonal glide is parallel to a face diagonal and has the symbol n.
A diamond glide (f.c.c) is parallel to the face diagonal and has the symbol d.
A diamond glide (b.c.c) is parallel to the body diagonal and has the symbol d. |
|
|
Term
| explain the statement k'-k = g. |
|
Definition
| This is another way of stating Bragg's law. k and k' have magnitudes of 1/lambda and g has a magnitude of 1/d. |
|
|
Term
| how are Intensity and structure factor related? |
|
Definition
|
|
Term
| What's the Schmidt factor? |
|
Definition
| cos(theta)cos(lambda); gives the shear on a slip plane in the slip direction. Slip occurs when Schmidt factor reaches a maximum |
|
|
Term
| How do you tell which slip direction, you have slip along using stereographic projection? (Diehl's rule) |
|
Definition
1) Identify the triangle containing the tensile axis
2) to find slip plane take {111} type pole and reflect across opposite side
3)to find the slip direction take the <110> type pole and reflect across the opposite side
4) this is for ccp crystals do opposite for bcc crystals; rather reflecting the <111> type pole will give you the direction etc.
5) tensile axis moves towards slip direction
6) once tensile direction reaches triangle side changes slip system |
|
|
Term
|
Definition
| a stereogram with its axes defined relative to the external frame of reference , and with particular hkl poles from each of the crystals in the polycrystalline aggregate plotted on it. |
|
|
Term
|
Definition
| pole figure in which the sample frame is plotted relative to the crystal axes of a reference crystal. |
|
|
Term
| How is crystallographic texture measured? |
|
Definition
| using a variety of techniques such as X-ray diffraction, EBSD |
|
|
Term
| What are some disadvantages of pole figures? Give an alternative method and define it. |
|
Definition
| They do not give information about the orientation of a particular crystal relative to another, since the poles are not identified with particular crystals in the final plot. Use an orientation distribution function which plots the euler angles |
|
|
Term
| Why does the the interfacial energy pf a tilt boundary as a function of misorientation angle not consistently rise with increasing theta? |
|
Definition
|
|
Term
| What is the General Rotation Matrix given a vector unit vector u = [u1 u2 u3] and an angle of rotation theta? |
|
Definition
let m = cos theta and n = sin theta
u1u1(1-m)+m u1u2(1-m)+u3n u1u3(1-m)-u2n
u1u2(1-m)-u3n u2u2(1-m)+m u2u3(1-m)+u1n
u1u3(1-m)+u2n u2u3(1-m)-u1n u3u3(1-m)+m |
|
|
Term
| How can you find the angle of rotation for an axis of rotation if you are given the general rotation matrix J? |
|
Definition
| J11+J22+j33 = 1+2cos(theta) |
|
|
Term
| What is the meaning of Epsilon in CSL notation? |
|
Definition
| 1/epsilon is the number of lattice sites common to both crystals out of the numbe rof total lattice point. |
|
|
Term
| What is Bain strain? What are the two inconsistencies associated with Bain strain? |
|
Definition
| The strain necessary to transformf.cc austenite into b.cc martensite. you would expect the |
|
|
