  We study the minimality properties of a new type of "soft" theta functions.
For a lattice $L\subset \mathbb{R}^d$, a $L$-periodic distribution of mass
$\mu_L$ and an other mass $\nu_z$ centred at $z\in \mathbb{R}^d$, we define,
for all scaling parameter $\alpha>0$, the translated lattice theta function
$\theta_{\mu_L+\nu_z}(\alpha)$ as the Gaussian interaction energy between
$\nu_z$ and $\mu_L$. We show that any strict local or global minimality result
that is true in the point case $\mu=\nu=\delta_0$ also holds for $L\mapsto
\theta_{\mu_L+\nu_0}(\alpha)$ and $z\mapsto \theta_{\mu_L+\nu_z}(\alpha)$ when
the measures are radially symmetric with respect to the points of $L\cup \{z\}$
and sufficiently rescaled around them (i.e. at a low scale). The minimality at
all scales is also proved when the radially symmetric measures are generated by
a completely monotone kernel. The method is based on a generalized Jacobi
transformation formula, some standard integral representations for lattice
energies and an approximation argument. Furthermore, for the honeycomb lattice
$\mathsf{H}$, the center of any primitive honeycomb is shown to minimize
$z\mapsto \theta_{\mu_{\mathsf{H}}+\nu_z}(\alpha)$ and many applications are
stated for other particular physically relevant lattices including the
triangular, square, cubic, orthorhombic, body-centred-cubic and
face-centred-cubic lattices.
