[Pw_forum] Requesting for structural details

[Huiqun Zhou]

You just need to pick up a math textbook of high school. 
Given a vector a = (ax, ay, az), |a| = sqrt(ax^2+ay^2+az^2).
For the angle between two vectors, you need to know their dot product,
cos(angle) = a dot b /(|a||b|), where a dot b = ax*bx + ay*by + az*bz.

Hope you know which two lattice vectors correspond to which angle.

zhou huiqun
@earth sciences, nanjing university, china

  ----- Original Message ----- 
  From: Kondaiah Samudrala 
  To: pw_forum at pwscf.org 
  Sent: Sunday, January 29, 2012 4:31 AM
  Subject: [Pw_forum] Requesting for structural details


  Dear All,

  I am working on layered type material which crystallizes in rhombohedral structure with space group 166 ( ibrav =5). In the i/p file for VC-Relax, i used the lattice parameters and angle as  celldm(1)=7.4870 and celldm(4)=0.586005.

  In the first step of the of the o/p file shows the basis vectors as 
  0.454970 -0.262677 0.850884
  0.000000 0.525354 0.850884
  -0.4504970 -0.262677 0.850884

  After completing the VC-Relax i got the basis vectors as


  CELL-PARAMETERS ( alat=7.4870)
  0.441119855 -0.254680667 0.78874941
  0.00000000   0.509361335 0.78874941
  -0.441119855 -0.254680667 0.78874941

    with this o/p values, how can i calculate lattice vector and angle for my material ( For orthorhombic and tetragonal structures i calculated lattice parametrs successfully but i am not able to do this structure ).


  i am requesting your favorable reply.

  with regards
  S.Appalakondaiah
  PhD Scholar
  University of Hyderabad
  Hyderabad
  India







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