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Foundations of mineralogy > Lecture one and two > Flashcards

Lecture one and two Flashcards

1
Q

What is a lattice?

A

A Lattice is a pattern of repeating points along which crystal unit cells can be arranged

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2
Q

What is the word to describe a set of repeating points along which a Crystal unit cell is placed

A

A lattice

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3
Q

What is a primitive unit cell

A

The unit cell which Only has lattice points in each corner

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4
Q

What is a Unit cell that only has lattice points in each corner called

A

A primitive unit cell

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5
Q

What is the atomic arrangement associated with a unit cell called

A

A motif

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6
Q

What is a motif?

A

The atomic arrangement associated with a unit cell

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7
Q

What components are required to describe the structure of an atomic arrangement

A

A lattice and a motif

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8
Q

What happens when you add a motif to a lattice

A

You get the whole atomic structure

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9
Q

How many arrangements of lattice points are possible?

A

Only five

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10
Q

What are the five possible arrangements of lattice points called

A

The primitive square lattice, the regular primitive lattice, The oblique P lattice, The rectangular centred lattice, and the hexagonal P lattice

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11
Q

What is a primitive square lattice

A

The sides are of equal length and the angle between the sides is 90°

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12
Q

What is a regular Primitive lattice

A

Besides can be of any length but the angle between the sides must always be 90°

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13
Q

What is an oblique p lattice

A

The sides can be of any length and it can have any angle between the sides except 90°

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14
Q

What is a rectangular centred lattice

A

It is the same as a regular primitive lattice except that it also has a lattice point in its centre

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15
Q

What is a hexagonal P lattice

A

A special form of the oblique P lattice with an angle between the sides of 60°

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16
Q

What is a symmetry element in a lattice

A

An element that when applied to a point on a lattice will restore the lattice to it’s original position

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17
Q

What fold of rotation symmetry can a lattice not have and why

A

Five-fold symmetry because a planar space cannot be filled with regular pentagons

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18
Q

What are the 4 symmetry elements of a lattice

A

Translation symmetry, mirror plane symmetry, glide Plane symmetry, and rotation symmetry

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19
Q

What is translation symmetry

A

Symmetry such that a point can be moved in a straight direction along the lattice maintaining its structure

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20
Q

What is mirror plane symmetry

A

Symmetry such that an element can be reflected over the line and maintain its structure

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21
Q

What is glide plane symmetry

A

Mirror Symmetry and translation symmetry in half steps form glide plane symmetry

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22
Q

What is rotation symmetry

A

Symmetry such that an object can be rotated around an axis a regular number of times maintaining its structure

23
Q

What is a triclinic system

A

A system where the three axes are not equal in length and the angles between the axes are not equal to each other

24
Q

What is a monoclinic system

A

A system where the axes are not equal in length and two of the angles between the axes are 90° while the third angle is greater than 90°

25
Q

What is an orthorhombic system

A

A system where the three axes are not equal in length but all of the angles between the axes are equal to 90°

26
Q

What is a Tetragonal system

A

A system Where two of the axes are equal in length and all of the angles between the axes are 90°

27
Q

What is a hexagonal system

A

A system with four axes such that three of the axes are of equal length and are spaced at 120° angles, Perpendicular to the fourth irregular axis

28
Q

What is an isometric system

A

A system such that the three axes are of equal length and at 90° to each other

29
Q

What are the three rules which assist in choosing the best definition of a unit cell

A

One the edges of the unit cell should coincide with the symmetry of the lattice. Two the edges of the unit cell should be related by the symmetry of the lattice. Three the smallest possible cell which contains all the elements should be chosen

30
Q

What are Vectorial properties

A

Properties of a crystal which depend on direction within the crystal

31
Q

Which coordinate axis does axis “a” Correspond with

A

The x axis

32
Q

Which coordinate axis does axis “b” Correspond with

A

The Y axis

33
Q

Which coordinate axis does axis “c” Correspond with

A

The Z axis

34
Q

Which two axes does angle alpha define

A

B and c

35
Q

Which two axes does angle beta define

A

A and c

36
Q

Which two axes does angle gamma define

A

A and B

37
Q

How many crystal systems are there

A

There are six crystal systems

38
Q

What are the six Crystal systems

A

Cubic or isometric system, tetragonal system, orthorhombic system, monoclinic system, triclinic system, and the trigonal or hexagonal system

39
Q

Do the 6 Crystal systems describe All of the variations of 3-D crystal arrangements?

A

No the six systems can also be primitive, face centred, or body centred, Such that the arrangement of lattice points upholds the rules of symmetry

40
Q

How many possible 3-D arrangements of lattices are there And what is this set called

A

14 Called the bravais lattices

41
Q

What are the two types of spaces between neighbouring spheres in stacked sheets called

A

Tetrahedral sites and octahedral sites

42
Q

What is a tetrahedral site

A

A space bound by four spheres where the centre of each of these spheres is joined to form a tetrahedron

43
Q

What is an octahedral site

A

A Space bound by six spheres where the centre of the spheres are joined to form an octahedron

44
Q

What is hexagonal close packing

A

An arrangement whereby the layers are repeated in an A.B. A.B. A.B. pattern

45
Q

What is cubic close packing

A

An arrangement where the layers I repeated in an A.B.C.A.B.C pattern

46
Q

What is body centred cubic packing

A

A way of stacking spheres such that the atoms only have eight neighbours

47
Q

What are the three types of Crystal symmetry

A

Planar symmetry, Axial symmetry, centres of symmetry

48
Q

What is planar symmetry

A

A plane of symmetry that divides a crystal into two similar halves such that one half is the mirror image of the other

49
Q

What is axial symmetry

A

A type of symmetry where a Crystal can be rotated around an axis in intervals where the original crystal shape and orientation is repeated

50
Q

What are the four types of Axial symmetry

A

A diad axis (two-fold) a triad axis (thee-fold) a tetrad axis (four-fold) and a hexad axis (six-fold)

51
Q

What are crystal centres of symmetry

A

An element of symmetry that is recognized when all like faces or edges of a crystal are arranged in pairs on opposite sides of a central point

52
Q

What are Miller indices

A

A system of defining Crystal faces, Developed by WH Miller in the 19th century which uses the unit cell of the Crystal and three points which cut the axes of that cell into ratios. Only the denominator of the ratios are displayed in a set enclosed by brackets.

53
Q

What Is a vector

A

A line which has both magnitude and direction

Foundations of mineralogy (2 decks)

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