<div dir="ltr"><br clear="all">Dear Developers/Users,<br><br> My name is Heena, and I am currently a beginner in the field of using the Thermo PW code for elastic constant determination. I am working on perovskite of type A2BB'X5, which is stable in the tetragonal phase.<br>I have encountered an issue in my calculations. While employing the Thermo PW code, I find that it generates seven elastic constants(Cij) instead of the six(Cij) (expected for tetragonal structure). below, I mention the obtained elastic constants for the same.<br>I am reaching out to seek guidance or assistance from anyone who may have experience with this code or a similar situation. It would be immensely grateful.<div><br></div><div><br></div><div>Elastic constants C_ij (kbar) <br>  i j=     1      2      3      4      5      6<br>  1  234.09216   54.10432  122.15608   0.00000   0.00000   0.00000<br>  2   54.10432  234.09216  122.15608   0.00000   0.00000   0.00000<br>  3  127.14759  127.14759  346.94234   0.00000   0.00000   0.00000<br>  4   0.00000   0.00000   0.00000   62.34926   0.00000   0.00000<br>  5   0.00000   0.00000   0.00000   0.00000   62.34926   0.00000<br>  6   0.00000   0.00000   0.00000   0.00000   0.00000   85.50041<br><br>   1 bar = 10^5 Pa; 10 kbar = 1 GPa; 1 atm = 1.01325 bar; 1 Pa = 1 N/m^2<br>   1 Pa = 10 dyn/cm^2; 1 Mbar = 10^11 Pa<br>   1 torr = 1 mm Hg = 1/760 bar = 7.5006 x 10^-3 Pa<br>          ----------------------------------------<br><br>   Elastic compliances  S_ij (1/Mbar) <br>  i j=     1      2      3      4      5      6<br>  1   5.29482   -0.26111   -1.77233   0.00000   0.00000   0.00000<br>  2   -0.26111   5.29482   -1.77233   0.00000   0.00000   0.00000<br>  3   -1.84475   -1.84475   4.18137   0.00000   0.00000   0.00000<br>  4   0.00000   0.00000   0.00000   16.03868   0.00000   0.00000<br>  5   0.00000   0.00000   0.00000   0.00000   16.03868   0.00000<br>  6   0.00000   0.00000   0.00000   0.00000   0.00000   11.69585<br><br><div>Thank you for your time and consideration.--<br></div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">Heena<div>Research scholar<div>JMI</div></div></div></div></div></div>