Suggestions on elastic constants and structural instability

[SGhosh]

Dear vasp users,
The following POSCAR was used for the calculation of elastic constant
Zr
1.00000000000000
5.0437426005754364 -0.0000000012348691 -0.0000000008666694
-0.0000000007223491 3.1479413133825997 -0.0000000001818763
-0.0000000014266610 -0.0000000007269031 8.7392682227392839
r
6
Direct
0.2499999998315977 0.5000000001553108 0.0833021399991757
0.7500000001778998 0.4999999996000770 0.9166976798440684
0.7500000001731231 0.0000000002695457 0.2499999618484108
0.2499999999434752 0.0000000002023256 0.7500001248149495
0.7500000000357215 0.4999999997878614 0.5833024699477438
0.2499999998381828 0.4999999999848795 0.4166976235456515

The IBRION tag was changed to 6 and POTIM to 0.010 with a k-point mesh size of 12x12x10. THE OUTCAR file shows

TOTAL ELASTIC MODULI (kBar)
Direction XX YY ZZ XY YZ ZX
--------------------------------------------------------------------------------
XX 1651.9858 461.1155 719.3759 0.2929 0.0149 -0.0528
YY 461.1155 1962.0596 463.4904 0.2974 -0.0201 -0.0229
ZZ 719.3759 463.4904 1651.0511 0.3004 -0.0144 0.0113
XY 0.2929 0.2974 0.3004 335.9460 0.0967 0.0014
YZ 0.0149 -0.0201 -0.0144 0.0967 335.7240 0.0027
ZX -0.0528 -0.0229 0.0113 0.0014 0.0027 465.5275
--------------------------------------------------------------------------------

Can anybody suggest on how to address the structural instability of the system.

Thank you
Suddhasattwa

[maartendft]

How do you know about the instability? Are there negative eigenvalues of the elastic matrix?