[Pw_forum] correction to my previous message ab. force constants

[Paolo Giannozzi]

On Saturday 16 April 2005 15:30, Bartek Wiendlocha wrote:

> 2. [...] if I sum FC(nb,na) over 'na' I'll get the total force constant for
> atom 'nb': k_j^i(nb) : F^i(nb) = - k_j^i(nb)*u_j(nb) which will give me
> total force (from interactions with all atoms in crystal) acting on 'nb' 
> in the direction i 'F^i(nb)' when moving atom 'nb' in the direction 'j' 
> with displacement 'u_j. 
> Now it seems more sensible for me, but i'm not sure. Please tell me
> if it's OK..

it looks ok to me, but it also seems to me that you get the same
information that is stored in the dynamical matrix at q=0 .

Everything is in atomic (Rydeberg) units: e^2=2, m=1/2, hbar=1
unless explicitely specified otherwise

Paolo

-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
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