# [Pw_forum] Requesting for structural details

Huiqun Zhou hqzhou at nju.edu.cn
Thu Feb 2 03:28:50 CET 2012

```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 ).

with regards
S.Appalakondaiah
PhD Scholar
India

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