Question

The unit cell in which the top face is partially sheared relative to the bottom face and in a direction parallel to one of the box edges is known as_______

(a) Orthorhombic unit cell

(b) Monoclinic unit cell

(c) Triclinic unit cell

(d) Trigon unit cell

The question was asked in class test.

Question is from Definitions topic in section X-Ray Diffraction of Solid State Chemistry

Answer 1

The correct answer is (b) Monoclinic unit cell

The explanation is: The monoclinic unit cell can be regarded as derived from orthorhombic shoebox by a shearing action in which the top face is partially sheared relative to the bottom face and in a direction parallel tone of the box edges, one of the angles departs from 90˚ and most of the symmetry is lost, apart from a mirror plane and/or a single twofold axis.