Crystallography Quiz: Parametral Plane & Face Flashcards

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Questions and Answers

What is the defining characteristic of a parametral plane?

It does not interact with any crystallographic axes.
It cuts two crystallographic axes.
It is parallel to one crystallographic axis.
It is parallel to all three crystallographic axes. (correct)

Which statement accurately describes the intercepts on crystallographic axes?

The intercept on b-axis is written after 'b' and on c-axis before 'c'.
The intercept on c-axis is written after 'c' and on a-axis before 'a'.
The intercepts are always measured with reference to the unit form's intercepts.
The intercept on a-axis is written after 'a' and on b-axis before 'b'. (correct)

What happens when a crystal face is parallel to a specific axis?

It cuts that axis at infinity. (correct)
It is considered as cutting that axis twice.
It does not interact with that axis.
It changes the crystal's symmetry.

What is a parametral plane in crystallography?

A plane that cuts all three crystallographic axes (B) Signup and view all the answers

How are the intercepts made by any face on the crystallographic axes described in the text?

They are always rational multiples of the intercepts made by the unit form (A) Signup and view all the answers

What does Hüvy’s law of rational indices state in crystallography?

The indices of crystal faces are determined by dividing the intercepts of the parametral plane and clearing fractions (D) Signup and view all the answers

What is the relationship between parameters and indices?

Indices are reciprocals of parameters (C) Signup and view all the answers

What does the parameter 0.374 (a):1 (b): 0.444 indicate about a crystal face?

Intersects a-axis at 0.374 units, b-axis at 1 unit, and is parallel to c-axis (A) Signup and view all the answers

How is the Weiss symbol represented for a crystal face parallel to the c-axis?

2a b ∞ c (A) Signup and view all the answers

How is a crystal face defined by indicating their intercepts on the crystallographic axes?

By indicating their lengths on the axes (A) Signup and view all the answers

Flashcards

Parametral Plane

A plane defined by its relationship to the crystallographic axes, vital for understanding crystal symmetry and habitual forms.

Intercepts on Crystallographic Axes

Points where a crystal face intersects the crystallographic axes, essential for describing crystal geometry in relative distances.

Parallel Crystal Face to an Axis

When a crystal face is parallel to an axis, it has an infinite intercept along that axis.

Hüvy's Law of Rational Indices

Indices of a crystal face are simple rational numbers; provides a systematic way to describe crystal orientation.

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Parameters and Indices Relationship

Parameters are actual distances, indices are derived numbers simplifying orientation description; understanding is crucial for crystal classification.

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Indication of Crystal Face with Parameter Format

Indicates intercept lengths of a crystal face along respective axes, aiding in visualizing spatial orientation.

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Defining Crystal Face by Intercepts

A crystal face can be defined by the exact intercepts it makes on the crystallographic axes, which inform its indices and overall geometry.

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Study Notes

Parametral Plane

A parametral plane is defined by its relationship to crystallographic axes, often characterized by specific intercepts.
It serves as an important concept in understanding crystal symmetry and habitual forms.

Intercepts on Crystallographic Axes

Intercepts are the points where a crystal face intersects the crystallographic axes, essential for describing crystal geometry.
These intercepts are expressed in terms of their relative distances along each axis.

Parallel Crystal Face to an Axis

When a crystal face is parallel to a specific axis, it has an infinite intercept along that axis, which influences its geometric properties.
This leads to simplifications in the description of the face's orientation.

Hüvy's Law of Rational Indices

Hüvy’s law states that the indices of a crystal face are simple rational numbers, providing a systematic way to describe crystal orientation.
This law is vital for categorizing and naming crystal forms.

Parameters and Indices Relationship

Parameters represent the actual distances along the crystallographic axes, while indices are derived numbers that describe the orientation in a simplified rational form.
A clear understanding of this relationship is crucial for identifying and classifying crystal faces.

Indication of Crystal Face with Parameter Format

The parameter format (e.g., 0.374 (a):1 (b):0.444) indicates the lengths of the intercepts made by a crystal face along the respective axes.
This notation helps in visualizing and interpreting the spatial orientation of the crystal face.

Weiss Symbol Representation

The Weiss symbol for a crystal face parallel to the c-axis is typically represented by a specific letter or combination reflecting its geometric relationship, enhancing communication within crystallography.

Defining Crystal Face by Intercepts

A crystal face can be defined by the exact intercepts it makes on the crystallographic axes, which inform its indices and overall geometry.
This method allows for a standardized approach to describing crystal forms.