[Pw_forum] how to obtained the eigndisplacement by eignvector in PWSCF
vsriniva at Princeton.EDU
Tue Jun 6 07:04:20 CEST 2006
Please correct me if I am wrong but to obtain the eigenvectors of the
dynamical matrix the values given by the code which are actually the normalized
eigen displacements cannot be directly used. For this purpose I usually
modify the code to print out the unnormalized eigen displacements and then multiply each component
with the sqaure root of the corresponding mass. The mass is taken in
Rydberg units. In these units the electron mass is 1/2.
On Tue, 6 Jun 2006, Stefano Baroni wrote:
> I do not quite get the question.
> It is the mass of Pb as found in any perdiodic table: 207.2 amu (see
> Atomic masses should also be specified in the "ATOMIC_SPECIES" card whose
> format, in the present case, should be something like:
> Pb 207.2 Pb_pseudopotential_file_name
> Are you confused instead by the negative value of the frequency? (this has
> nothing to do with masses)
> Hope this helps - Stefano
> On Jun 5, 2006, at 4:23 PM, éå¶ æ± wrote:
>> Dear all user:
>> i have calculated the phonon of PbTiO3, and i have obtained eignvector of
>> atom under each mode.
>> for example:
>> omega( 1) = -4.221301 [THz] = -140.808368 [cm-1]
>> ( -0.092855 0.000000 -0.004178 0.000000 0.001020 0.000000 )
>> ( -0.185613 0.000000 -0.008352 0.000000 0.002040 0.000000 )
>> ( 0.598322 0.000000 0.026924 0.000000 -0.005371 0.000000 )
>> ( 0.598322 0.000000 0.021990 0.000000 -0.006576 0.000000 )
>> ( 0.488678 0.000000 0.026924 0.000000 -0.006576 0.000000 )
>> now i have kown the eigndisplacement |u> = M^(-1/2) | v>.
>> but i am confused with mass M. for example, for Pb atom in PbTiO3. how much
>> is mass of Pb in equation above?
>> please grive me some construction!
> Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste
> [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)
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