[Wien] Question about ELAST

[長谷泉]

Dear Wien2k Users,


Hello, I have a question about ELAST, which calculates the elastic constants for cubic lattice.

I made a test calculation for NaCl (fcc). I used default settings (#k=1000, Vxc=PBE, RKmax=7.0, rmt=2.5 for Na and Cl).

And I used the default values for eos/tetra/rhomb.job .


For eos I got reasonable value (B_cal=29.7GPa while B_exp=24.4GPa). However, for tet and rhomb  I got very abnormal values. I obtained unphysical C44<0, while C44_exp=12.6GPa.


Especially for tet, E(x) is too soft, not harmonic, and even not symmetric.

I show tetra.output as follows:


Polynomial fit or tetragonal strain done

A RMS of 0.203369E-12 was achieved using a polynome of degree :  4


At volume=    301.07 bohr^3

C11-C12 is: 0.000062 a.u or     0.915 GPa


         Strain       energy          dE

    0.00675692  -1248.135736  0.227374E-12

    0.01370014  -1248.135102  0.227374E-12

   -0.00000019  -1248.135686  0.227374E-12

   -0.00657965  -1248.135568  0.227374E-12

   -0.01298805  -1248.135200  0.000000E+00


I changed the lattice constant slightly, and for P~0.1GPa I got almost the same result.



As for MgO which has the same crystal structure with NaCl, I obtained almost the same values as the UsersGuide by T.Charpin, 12th July 2001.


Any kind of help will be greatly appreciated.


Best Regards,



Izumi Hase

National Institute of Advanced Industrial Science and Technology (AIST), Japan


tel: 029-861-5147  fax: 029-861-5569

e-mail:   i.hase at aist.go.jp

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