The ABINIT Users Mailing List ( CLOSED )

[whoming@sohu.com]

Dear Mikami-san,

>Dear Whoming,

>As I told you in previous personal correspondence,

... Many thanks for your kind help!

>- please have fully optimized geometry with your pseudoPP calc.
>the lattice constants/internal coordinates should be fully
>optimized with your PPs.
>Your PPs may differ with the PPs adopted there...

... Ok, I will try to optimize the geometry. My used PP is the LDA
Troullier-Matins type.

>- You misunderstand the LO-TOs.
>Eu is like the mode in ab-plane, and A2u mode // c-axis.
>If q // c, Eu mode is TO, and A2u mode is LO.
>If q // ab-plane, Eu will be splitted into LO+TO, and A2u mode is TO.
>(Then, the rest is your homework ... )

... Yes, I can understand this. I have just post a correction to this
mailing-list.

>The paper says "the optical modes at Gamma are classified into
>2A1g + 2 Eg + 2A2u + 2Eu". It never says, "8 IR modes were
>reported including 4 Eu and 4 Au modes" (This is your mental picture !)
>Please cite correctly... :-(

... In your paper you state "The present calculation thus predicts the
existence of eight IR modes for Y2O2S (Table I)." Page 2, Right Column, 
Line 16 from the bottom. I mean that 4 frequencies labled Eu and 4 labled
A2u in Table. I.

But when I writting here, I know what the meaning of 8 IR-active modes is:
When E//a,b the IR-active modes are:
A2u symmetry TO modes, 315.3 cm-1, 475.2 cm-1;
Eu symmetry  TO modes, 235.7 cm-1, 485.2 cm-1;
             LO modes, 266.3 cm-1, 599.6 cm-1;
here totally 6 modes;

When E//c, the IR-active modes are
A2u symmetry LO modes, 360.9 cm-1, 587.4 cm-1;
Eu  symmetry TO modes, 235.7 cm-1, 485.2 cm-1.

Noticed that the Eu's TO modes having the same frequecies no matter E//c
or E//a,b, the total number of IR-active modes are 8?

Am I right?


>Please let me refrain:
>"It is only with the heart that one can see rightly; what is essential is 
>>invisible to the eye."
>("On ne voit bien qu'avec le coeur. L'essentiel est invisible pour les 
>yeux.")
>You might want to consult with chapters on phonon in some textbooks. ;-)
>(There is no royal road ... )

... Thanks for your patience.

Whoming

>Masayoshi