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Degree 1 serendipity H(div) on a hexahedron

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In this example:
\(\displaystyle l_{0}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{0}}\boldsymbol{v}\cdot(- s_{0} - t_{1} + 1)\hat{\boldsymbol{n}}_{0}\)
where \(f_{0}\) is the 0th face;
and \(\hat{\boldsymbol{n}}_{0}\) is the normal to facet 0.

\(\displaystyle \boldsymbol{\phi}_{0} = \left(\begin{array}{c}\displaystyle 3 x \left(1 - x\right)\\\displaystyle 3 y \left(1 - y\right)\\\displaystyle 6 x z - 6 x + 6 y z - 6 y - 7 z + 7\end{array}\right)\)

This DOF is associated with face 0 of the reference element.
\(\displaystyle l_{1}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{0}}\boldsymbol{v}\cdot(s_{0})\hat{\boldsymbol{n}}_{0}\)
where \(f_{0}\) is the 0th face;
and \(\hat{\boldsymbol{n}}_{0}\) is the normal to facet 0.

\(\displaystyle \boldsymbol{\phi}_{1} = \left(\begin{array}{c}\displaystyle 3 x \left(x - 1\right)\\\displaystyle 3 y \left(1 - y\right)\\\displaystyle - 6 x z + 6 x + 6 y z - 6 y - z + 1\end{array}\right)\)

This DOF is associated with face 0 of the reference element.
\(\displaystyle l_{2}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{0}}\boldsymbol{v}\cdot(s_{1})\hat{\boldsymbol{n}}_{0}\)
where \(f_{0}\) is the 0th face;
and \(\hat{\boldsymbol{n}}_{0}\) is the normal to facet 0.

\(\displaystyle \boldsymbol{\phi}_{2} = \left(\begin{array}{c}\displaystyle 3 x \left(1 - x\right)\\\displaystyle 3 y \left(y - 1\right)\\\displaystyle 6 x z - 6 x - 6 y z + 6 y - z + 1\end{array}\right)\)

This DOF is associated with face 0 of the reference element.
\(\displaystyle l_{3}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{1}}\boldsymbol{v}\cdot(- s_{0} - t_{1} + 1)\hat{\boldsymbol{n}}_{1}\)
where \(f_{1}\) is the 1st face;
and \(\hat{\boldsymbol{n}}_{1}\) is the normal to facet 1.

\(\displaystyle \boldsymbol{\phi}_{3} = \left(\begin{array}{c}\displaystyle 3 x \left(x - 1\right)\\\displaystyle - 6 x y + 6 x - 6 y z + 7 y + 6 z - 7\\\displaystyle 3 z \left(z - 1\right)\end{array}\right)\)

This DOF is associated with face 1 of the reference element.
\(\displaystyle l_{4}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{1}}\boldsymbol{v}\cdot(s_{0})\hat{\boldsymbol{n}}_{1}\)
where \(f_{1}\) is the 1st face;
and \(\hat{\boldsymbol{n}}_{1}\) is the normal to facet 1.

\(\displaystyle \boldsymbol{\phi}_{4} = \left(\begin{array}{c}\displaystyle 3 x \left(1 - x\right)\\\displaystyle 6 x y - 6 x - 6 y z + y + 6 z - 1\\\displaystyle 3 z \left(z - 1\right)\end{array}\right)\)

This DOF is associated with face 1 of the reference element.
\(\displaystyle l_{5}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{1}}\boldsymbol{v}\cdot(s_{1})\hat{\boldsymbol{n}}_{1}\)
where \(f_{1}\) is the 1st face;
and \(\hat{\boldsymbol{n}}_{1}\) is the normal to facet 1.

\(\displaystyle \boldsymbol{\phi}_{5} = \left(\begin{array}{c}\displaystyle 3 x \left(x - 1\right)\\\displaystyle - 6 x y + 6 x + 6 y z + y - 6 z - 1\\\displaystyle 3 z \left(1 - z\right)\end{array}\right)\)

This DOF is associated with face 1 of the reference element.
\(\displaystyle l_{6}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{2}}\boldsymbol{v}\cdot(- s_{0} - t_{1} + 1)\hat{\boldsymbol{n}}_{2}\)
where \(f_{2}\) is the 2nd face;
and \(\hat{\boldsymbol{n}}_{2}\) is the normal to facet 2.

\(\displaystyle \boldsymbol{\phi}_{6} = \left(\begin{array}{c}\displaystyle 6 x y + 6 x z - 7 x - 6 y - 6 z + 7\\\displaystyle 3 y \left(1 - y\right)\\\displaystyle 3 z \left(1 - z\right)\end{array}\right)\)

This DOF is associated with face 2 of the reference element.
\(\displaystyle l_{7}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{2}}\boldsymbol{v}\cdot(s_{0})\hat{\boldsymbol{n}}_{2}\)
where \(f_{2}\) is the 2nd face;
and \(\hat{\boldsymbol{n}}_{2}\) is the normal to facet 2.

\(\displaystyle \boldsymbol{\phi}_{7} = \left(\begin{array}{c}\displaystyle - 6 x y + 6 x z - x + 6 y - 6 z + 1\\\displaystyle 3 y \left(y - 1\right)\\\displaystyle 3 z \left(1 - z\right)\end{array}\right)\)

This DOF is associated with face 2 of the reference element.
\(\displaystyle l_{8}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{2}}\boldsymbol{v}\cdot(s_{1})\hat{\boldsymbol{n}}_{2}\)
where \(f_{2}\) is the 2nd face;
and \(\hat{\boldsymbol{n}}_{2}\) is the normal to facet 2.

\(\displaystyle \boldsymbol{\phi}_{8} = \left(\begin{array}{c}\displaystyle 6 x y - 6 x z - x - 6 y + 6 z + 1\\\displaystyle 3 y \left(1 - y\right)\\\displaystyle 3 z \left(z - 1\right)\end{array}\right)\)

This DOF is associated with face 2 of the reference element.
\(\displaystyle l_{9}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{3}}\boldsymbol{v}\cdot(- s_{0} - t_{1} + 1)\hat{\boldsymbol{n}}_{3}\)
where \(f_{3}\) is the 3th face;
and \(\hat{\boldsymbol{n}}_{3}\) is the normal to facet 3.

\(\displaystyle \boldsymbol{\phi}_{9} = \left(\begin{array}{c}\displaystyle x \left(- 6 y - 6 z + 7\right)\\\displaystyle 3 y \left(y - 1\right)\\\displaystyle 3 z \left(z - 1\right)\end{array}\right)\)

This DOF is associated with face 3 of the reference element.
\(\displaystyle l_{10}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{3}}\boldsymbol{v}\cdot(s_{0})\hat{\boldsymbol{n}}_{3}\)
where \(f_{3}\) is the 3th face;
and \(\hat{\boldsymbol{n}}_{3}\) is the normal to facet 3.

\(\displaystyle \boldsymbol{\phi}_{10} = \left(\begin{array}{c}\displaystyle x \left(6 y - 6 z + 1\right)\\\displaystyle 3 y \left(1 - y\right)\\\displaystyle 3 z \left(z - 1\right)\end{array}\right)\)

This DOF is associated with face 3 of the reference element.
\(\displaystyle l_{11}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{3}}\boldsymbol{v}\cdot(s_{1})\hat{\boldsymbol{n}}_{3}\)
where \(f_{3}\) is the 3th face;
and \(\hat{\boldsymbol{n}}_{3}\) is the normal to facet 3.

\(\displaystyle \boldsymbol{\phi}_{11} = \left(\begin{array}{c}\displaystyle x \left(- 6 y + 6 z + 1\right)\\\displaystyle 3 y \left(y - 1\right)\\\displaystyle 3 z \left(1 - z\right)\end{array}\right)\)

This DOF is associated with face 3 of the reference element.
\(\displaystyle l_{12}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{4}}\boldsymbol{v}\cdot(- s_{0} - t_{1} + 1)\hat{\boldsymbol{n}}_{4}\)
where \(f_{4}\) is the 4th face;
and \(\hat{\boldsymbol{n}}_{4}\) is the normal to facet 4.

\(\displaystyle \boldsymbol{\phi}_{12} = \left(\begin{array}{c}\displaystyle 3 x \left(1 - x\right)\\\displaystyle y \left(6 x + 6 z - 7\right)\\\displaystyle 3 z \left(1 - z\right)\end{array}\right)\)

This DOF is associated with face 4 of the reference element.
\(\displaystyle l_{13}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{4}}\boldsymbol{v}\cdot(s_{0})\hat{\boldsymbol{n}}_{4}\)
where \(f_{4}\) is the 4th face;
and \(\hat{\boldsymbol{n}}_{4}\) is the normal to facet 4.

\(\displaystyle \boldsymbol{\phi}_{13} = \left(\begin{array}{c}\displaystyle 3 x \left(x - 1\right)\\\displaystyle y \left(- 6 x + 6 z - 1\right)\\\displaystyle 3 z \left(1 - z\right)\end{array}\right)\)

This DOF is associated with face 4 of the reference element.
\(\displaystyle l_{14}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{4}}\boldsymbol{v}\cdot(s_{1})\hat{\boldsymbol{n}}_{4}\)
where \(f_{4}\) is the 4th face;
and \(\hat{\boldsymbol{n}}_{4}\) is the normal to facet 4.

\(\displaystyle \boldsymbol{\phi}_{14} = \left(\begin{array}{c}\displaystyle 3 x \left(1 - x\right)\\\displaystyle y \left(6 x - 6 z - 1\right)\\\displaystyle 3 z \left(z - 1\right)\end{array}\right)\)

This DOF is associated with face 4 of the reference element.
\(\displaystyle l_{15}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{5}}\boldsymbol{v}\cdot(- s_{0} - t_{1} + 1)\hat{\boldsymbol{n}}_{5}\)
where \(f_{5}\) is the 5th face;
and \(\hat{\boldsymbol{n}}_{5}\) is the normal to facet 5.

\(\displaystyle \boldsymbol{\phi}_{15} = \left(\begin{array}{c}\displaystyle 3 x \left(x - 1\right)\\\displaystyle 3 y \left(y - 1\right)\\\displaystyle z \left(- 6 x - 6 y + 7\right)\end{array}\right)\)

This DOF is associated with face 5 of the reference element.
\(\displaystyle l_{16}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{5}}\boldsymbol{v}\cdot(s_{0})\hat{\boldsymbol{n}}_{5}\)
where \(f_{5}\) is the 5th face;
and \(\hat{\boldsymbol{n}}_{5}\) is the normal to facet 5.

\(\displaystyle \boldsymbol{\phi}_{16} = \left(\begin{array}{c}\displaystyle 3 x \left(1 - x\right)\\\displaystyle 3 y \left(y - 1\right)\\\displaystyle z \left(6 x - 6 y + 1\right)\end{array}\right)\)

This DOF is associated with face 5 of the reference element.
\(\displaystyle l_{17}:\boldsymbol{v}\mapsto\displaystyle\int_{f_{5}}\boldsymbol{v}\cdot(s_{1})\hat{\boldsymbol{n}}_{5}\)
where \(f_{5}\) is the 5th face;
and \(\hat{\boldsymbol{n}}_{5}\) is the normal to facet 5.

\(\displaystyle \boldsymbol{\phi}_{17} = \left(\begin{array}{c}\displaystyle 3 x \left(x - 1\right)\\\displaystyle 3 y \left(1 - y\right)\\\displaystyle z \left(- 6 x + 6 y + 1\right)\end{array}\right)\)

This DOF is associated with face 5 of the reference element.