GATE XE concept:unit-cells PYQs & Answers

Questions 1–6 of 6. Imported answers require independent review unless marked reviewed.

Consider 3 crystals (all having FCC lattice) labeled as P, Q and R as described below:

Crystal P: Cu crystal with 4 Cu atoms per unit cell Crystal Q: NaCl crystal with 4 Na⁺ ions and 4 Cl⁻ ions per unit cell Crystal R: Diamond crystal with 8 C atoms per unit cell

Which of the following options is/are correct?

Your answerSelect all correct options. You can choose more than one.

Only crystal P is a close packed structure.

Only crystal Q is a close packed structure.

Crystal R has the smallest packing factor.

All the crystals P, Q and R are close packed structures.

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The figure below shows a plane PQR in a unit cell. The Miller indices of the plane PQR is

Diagram for Engineering Sciences question 44

Your answerChoose one option.

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Which one of the following unit cell parameters represents a tetragonal crystal system?

Your answerChoose one option.

a = b = c ; α = β = γ ≠ 90°

a ≠ b ≠ c ; α = β = γ = 90°

a = b ≠ c ; α = β = 90°, γ = 120°

a = b ≠ c ; α = β = γ = 90°

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The Miller indices for the shaded plane shown in the unit cell below is

Diagram for Engineering Sciences question 55

Your answerChoose one option.

[632]

[123]

(632)

(123)

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Among the 14 Bravais lattices, there is no base centred cubic unit cell. Which of the following statement(s) is/are true?

Your answerSelect all correct options. You can choose more than one.

The base-centred cubic unit cell is same as the simple tetragonal unit cell

The base-centred cubic unit cell is same as the body centred tetragonal unit cell

The base-centred cubic unit cell is same as the simple orthorhombic unit cell

The base-centred cubic unit cell does not have any 3-fold rotation axis

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The unit cell volume of polyethylene (PE) is 0.093 nm

. Assuming two ethylene repeat units are contained within each unit cell, the density of a totally crystalline PE will be .............. g/cm

(Take the atomic weights for carbon and hydrogen as 12.01 g/mol and 1.008 g/mol, respectively, and the Avogadro’s number as

repeat units/mol)

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GATE XE concept:unit-cells PYQs

How to practice concept:unit-cells

Question 58

Question 44

Question 48

Question 55

Question 58

Question 43