[Wien] Total Energy Calculations involving Chlorides

[Ghosh SUDDHASATTWA]

Dear Wien2k users, 

I have posted this question last week. Unfortunately, I could not get any
suggestions. I ask this again. 

Which functional LDA or GGA is good for total energy calculations for
compounds like NaCl, CsCl. I would like to estimate the enthalpies of some
mixed salts like (Na,Cs)Cl. If we see the enthalpy equation for NaCl, we
have 

Enthalpy_NaCl= ENE (NaCl)-1/2*ENE (Na)-1/4*ENE(Cl2)

 

How do we estimate the third term on the right? Which functional? 

 

I did the following calculation 

I placed a chlorine atom in P4/mmm cell at (0,0,0.0606) with a sufficiently
large lattice parameters and did the SCF with a single gamma point. 

I got ENE=-1845.995 Ry

I then placed a Cl atom in a Fm3m cell at (0,0,0) and did the calculation
for a single gamma point. I got ENE=-922.872 

The dissociation energy comes to be -330 kJ/mol which actually is -242.602
kJ/mol. 

 

So , how do we estimate E(Cl2) for getting accurate enthalpies of NaCl. 

Any suggestions please 

 

Thanks 

Suddhasattwa 

 

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