# Example: Elastic tensor¶

```
#! /bin/sh
# === Diamond ===
AMS_JOBNAME=Diamond $AMSBIN/ams << EOF
Task GeometryOptimization
Properties
ElasticTensor Yes
End
System
Atoms
C 0.44625 0.44625 2.23125
C 2.23125 2.23125 2.23125
C -2.23125 -2.23125 -2.23125
C -0.44625 -0.44625 -2.23125
C -0.44625 -2.23125 -0.44625
C 1.33875 -0.44625 -0.44625
C -2.23125 -0.44625 -0.44625
C -0.44625 1.33875 -0.44625
C -0.44625 -0.44625 1.33875
C 1.33875 1.33875 1.33875
C -1.33875 -1.33875 -1.33875
C 0.44625 0.44625 -1.33875
C 0.44625 -1.33875 0.44625
C 2.23125 0.44625 0.44625
C -1.33875 0.44625 0.44625
C 0.44625 2.23125 0.44625
End
Lattice
0.0 3.57 3.57
3.57 0.0 3.57
3.57 3.57 0.0
End
End
GeometryOptimization
OptimizeLattice Yes
Convergence Quality=Good
End
Symmetry Tolerance=1e-6
Engine DFTB
Model DFTB
ResourcesDir DFTB.org/mio-1-1
KSpace
Type Symmetric
Symmetric KInteg=3
End
Technical AnalyticalStressTensor=False # Not yet supported with symmetric k-space grid.
EndEngine
EOF
# === Boron-Nitride sheet ===
# 3x3 super-cell, default k-space sampling
AMS_JOBNAME=BN_sheet $AMSBIN/ams << EOF
Task GeometryOptimization
Properties
ElasticTensor Yes
End
System
Atoms
N 3.76095075 0.723795 0.0
N 5.01460112 2.89518114 0.0
B -3.76095112 -2.17138614 0.0
B -2.50730075 0.0 0.0
B -1.25365038 2.17138614 0.0
B -1.25365037 -2.17138614 0.0
B 0.0 0.0 0.0
B 1.25365037 2.17138614 0.0
B 1.25365038 -2.17138614 0.0
B 2.50730075 0.0 0.0
B 3.76095112 2.17138614 0.0
N -2.50730112 -1.44759114 0.0
N -1.25365075 0.723795 0.0
N -3.8e-07 2.89518114 0.0
N -3.7e-07 -1.44759114 0.0
N 1.25365 0.723795 0.0
N 2.50730037 2.89518114 0.0
N 2.50730038 -1.44759114 0.0
End
Lattice
7.52190225 0.0
3.76095111 6.51415842
End
End
GeometryOptimization
OptimizeLattice Yes
Convergence Quality=Good
End
Engine DFTB
Model SCC-DFTB
ResourcesDir DFTB.org/matsci-0-3
EndEngine
EOF
# === Polyoxyethylene ===
# primitive cell with k-space sampling
AMS_JOBNAME=Polyoxyethylene $AMSBIN/ams << EOF
Task GeometryOptimization
Properties
ElasticTensor Yes
End
ElasticTensor
StrainStepSize 0.002
End
System
Atoms
C -0.279368361 -0.125344097 -0.026221791
O 0.840592835 -0.919621431 -0.193214154
H -0.279527057 0.337014408 0.997733792
H -0.281697417 0.707951120 -0.778297849
End
Lattice
2.240292981
End
End
GeometryOptimization
OptimizeLattice Yes
Convergence Quality=Good
End
Engine DFTB
Model SCC-DFTB
ResourcesDir DFTB.org/3ob-3-1
KSpace
Type Symmetric
Symmetric KInteg=5
End
Technical AnalyticalStressTensor=False # Not yet supported with symmetric k-space grid.
EndEngine
EOF
# Note: the elastic tensor is also printed to standard output.
echo ""
echo "Extract the elastic tensor of Diamond from the rkf file:"
$AMSBIN/amsreport Diamond.results/dftb.rkf -r "AMSResults%ElasticTensor#12.4f##6"
echo ""
echo "Extract the elastic tensor of Boron-Nitride from the rkf file:"
$AMSBIN/amsreport BN_sheet.results/dftb.rkf -r "AMSResults%ElasticTensor#12.4f##3"
echo ""
echo "Extract the elastic tensor of Polyoxyethylene from the rkf file:"
$AMSBIN/amsreport Polyoxyethylene.results/dftb.rkf -r "AMSResults%ElasticTensor#12.4f##1"
```