[CPMD-list] About geometry optimization

[naivebamboo Huang]

Dear CPMD users,
      I am a novice to CPMD. I am trying to optimize the geometry of Bi2Te3 
and have some questions for the geometry optimization:
1. My understanding for the optimization of geometry is that if only 
"optimize geometry"  is used, the symmetry and the lattice constant of the 
cell will not change and only the coordinates of atoms in the cell are 
changed. Is this correct?

2. If I want to do the global optimization for both the lattice constant and 
the coordinates of atoms, should I just add "STEEPEST DESCENT CELL" except 
"OPTIMIZE GEOMETRY"?

3.The atoms in the cell are charged and the electrostatic interaction is 
important for Bi2Te3. So if I try the geometry optimization, since the 
cut-off radius of the electrostatic interaction is around 12 Angstrom, do I 
need to choose a large cell to include the effects of this long-range 
interactions? or I can just use the primitive cell.

4. I would like to get the force constants  for each two-body bond with the 
optimal geometry for later calculations. But the atoms in a primitive cell 
are always bonded with the atoms in another primitive cell. If I get the 
force constant matrix, does it correspond the bonded two atoms? or just 
correponds to the atoms in the same primitive cell?

Thanks a lot

Baoling Huang

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