UPSC Combined Geo-Scientist, Mains · 2022 · Mains Paper I

Q2(a). Two perovskite unit-cell origins

10 marks
Topic: Inorganic solids
Answered

Question

Perovskite mineral contains calcium, titanium and oxygen. (i) Draw the unit cell of perovskite with titanium at the centre of the unit cell. (ii) Draw the unit cell of perovskite with calcium at the centre of the unit cell. (iii) Find the formula of perovskite in both the unit cell representations. (iv) What is the coordination number of titanium in each representation of the unit cell?

Answer in brief

Both origin choices give CaTiO₃. Ti has six nearest oxygen neighbours in both; shifting the origin does not change coordination.

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Topic notes: inorganic solids: perovskite, spinel, ReO₃, corundum, high-Tc superconductors and solid-state synthesis, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversperovskite structureCaTiO3 unit cellABO3coordination numberorigin shift

All parts of Question 2

2(a) Two perovskite unit-cell origins10 marks
2(b) Increasing silicon conductivity10 marks
2(c) Fullerite basis and ammonolysis4 marks
2(d) Defects and solid-state properties6 marks