[Pw_forum] fermi energy

[Stefano Baroni]

Hi Rudra: I am a bit embarassed by your question:

On Jan 25, 2008, at 1:43 PM, Rudra Banerjee wrote:

> when i am plotting band structure for non-metallic molecules,

do molecules display any band structure?
(I thought the very concept of energy bands would apply to infinite  
systems, which molecules are not)

how would you distinguish a metallic molecule from a non metallic one?
(again, being a metal or an insulator is a property of extended  
systems, not of molecules)

> how should i choose fermi energy?

for an infinite system, at zero temperature the fermi energy is ill  
defined and may be chosen anywhere in the energy gap. at small T, it  
lies at mid gap

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Stefano Baroni

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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
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