From f6bdf5662ec9af4f0eefcfc31fe4c61ba1d1bd10 Mon Sep 17 00:00:00 2001
From: "Jibril B. Coulibaly"
 <43829860+jibril-b-coulibaly@users.noreply.github.com>
Date: Fri, 6 Dec 2019 10:40:04 -0600
Subject: [PATCH] Update pair_granular.rst

Correct formula for tangent stiffness, consistent with `PairGranular::mix_stiffnessG()`
---
 doc/src/pair_granular.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/src/pair_granular.rst b/doc/src/pair_granular.rst
index d5f522462d..294bec9b8c 100644
--- a/doc/src/pair_granular.rst
+++ b/doc/src/pair_granular.rst
@@ -432,7 +432,7 @@ option by an additional factor of *a*\ , the radius of the contact region. The t
 Here, *a* is the radius of the contact region, given by :math:`a =\sqrt{R\delta}`
 for all normal contact models, except for *jkr*\ , where it is given
 implicitly by :math:`\delta = a^2/R - 2\sqrt{\pi \gamma a/E}`, see
-discussion above. To match the Mindlin solution, one should set :math:`k_t = 8G`, where :math:`G` is the shear modulus, related to Young's modulus
+discussion above. To match the Mindlin solution, one should set :math:`k_t = 4G/(2-\nu)`, where :math:`G` is the shear modulus, related to Young's modulus
 :math:`E` by :math:`G = E/(2(1+\nu))`, where :math:`\nu` is Poisson's ratio. This
 can also be achieved by specifying *NULL* for :math:`k_t`, in which case a
 normal contact model that specifies material parameters :math:`E` and