Solution Callister 7- ... Ciência dos Materiais - callister7e sm ch03 13, Manuais, Projetos, Pesquisas de Física

Baixe Solution Callister 7- ... Ciência dos Materiais - callister7e sm ch03 13 e outras Manuais, Projetos, Pesquisas em PDF para Física, somente na Docsity! 3-15 3.13 In order to determine whether Nb has an FCC or a BCC crystal structure, we need to compute its density for each of the crystal structures. For FCC, n = 4, and a = 2 R 2 (Equation 3.1). Also, from Figure 2.6, its atomic weight is 92.91 g/mol. Thus, for FCC (employing Equation 3.5) ρ = nANb a3N A = nANb (2R 2)3N A = (4 atoms/unit cell)(92.91 g/mol) (2)(1.43 × 10-8 cm)( 2)[ ]3 /(unit cell)⎧ ⎨ ⎩ ⎫ ⎬ ⎭ (6.023 × 1023 atoms /mol) = 9.33 g/cm3 For BCC, n = 2, and a = 4 R 3 (Equation 3.3), thus ρ = nANb 4 R 3 ⎛ ⎝ ⎜ ⎜ ⎞ ⎠ ⎟ ⎟ 3 N A ρ = (2 atoms/unit cell)(92.91 g/mol) (4)(1.43 × 10-8 cm) 3 ⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ 3 /(unit cell) ⎧ ⎨ ⎪ ⎩ ⎪ ⎫ ⎬ ⎪ ⎭ ⎪ (6.023 × 1023 atoms /mol) = 8.57 g/cm3 which is the value provided in the problem statement. Therefore, Nb has a BCC crystal structure. Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instructional purposes only to students enrolled in courses for which the textbook has been adopted. Any other reproduction or translation of this work beyond that permitted by Sections 107 or 108 of the 1976 United States Copyright Act without the permission of the copyright owner is unlawful.