1 / 10

MATERIALS SCIENCE & ENGINEERING

MATERIALS SCIENCE & ENGINEERING . Part of . A Learner’s Guide. AN INTRODUCTORY E-BOOK. Anandh Subramaniam & Kantesh Balani Materials Science and Engineering (MSE) Indian Institute of Technology, Kanpur- 208016 Email: anandh@iitk.ac.in, URL: home.iitk.ac.in/~anandh.

farsiris
Télécharger la présentation

MATERIALS SCIENCE & ENGINEERING

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MATERIALS SCIENCE & ENGINEERING Part of A Learner’s Guide AN INTRODUCTORY E-BOOK Anandh Subramaniam & Kantesh Balani Materials Science and Engineering (MSE) Indian Institute of Technology, Kanpur- 208016 Email:anandh@iitk.ac.in, URL:home.iitk.ac.in/~anandh http://home.iitk.ac.in/~anandh/E-book.htm

  2. Mystery of the missing entries in the Bravais List!  Few illustrations • Another point of view:There are 7 crystal systemsEach of them “can have” P, I, F, C type lattice (4 types)Hence the “potential” number is (7  4) = 28But 14 of these are only distinct Points to note: • Every lattice that you can construct is present somewhere in the list  the issue is where to put them • Concept of choice of unit cell is also invoked along with the classification of Bravais lattices • The factors which are taken to into account are (like for the unit cell): Symmetry Size

  3. What we choose Mystery of the missing entries in the Bravais List! But then Cubic crystals need not have any 4-fold axes!!(cubic lattices do need to have!) Hence Cannot be called Cubic Hence even though this lattice remains as it is  it is called Simple Tetragonal(which is smaller in size)

  4. What we choose Mystery of the missing entries in the Bravais List! Smaller sized Body Centred Cell is chosen FCT = BCT Face Centred Tetragonal = Body Centred Tetragonal

  5. What we choose Mystery of the missing entries in the Bravais List! Smaller sized Simple Cell is chosen CCT = ST C Centred Tetragonal = Simple Tetragonal

  6. Mystery of the missing entries in the Bravais List! Putting a lattice point at body centre destroys the 6-fold axis Hence body centred hexagonal lattice NOT possible

  7. Mystery of the missing entries in the Bravais List! Putting a lattice point at body centre destroys the 6-fold axis

  8. Mystery of the missing entries in the Bravais List! Putting a lattice point at body centre destroys the 6-fold axis

  9. & what we don’t Mystery of the missing entries in the Bravais List! Cubic F  Tetragonal I(not chosen) As the FCC lattice has higher symmetry than the BCT cell(the one with higher symmetry is chosen)

  10. Some example of the allowed and disallowed transfers • Crystal system Bravais lattices • Cubic P I F C • Tetragonal P I F • Orthorhombic P I F C • Hexagonal P • Trigonal P • Monoclinic P C • Triclinic P x Slide Courtesy Dr. Rajesh Prasad

More Related