From 26427cc4cbd27ee99517492cc8578aa441a078ec Mon Sep 17 00:00:00 2001
From: Aidan Thompson <athomps@sandia.gov>
Date: Tue, 1 Oct 2019 11:40:21 -0600
Subject: [PATCH] Fixed error in neighbor distance check for box dimensions

---
 src/neighbor.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/neighbor.cpp b/src/neighbor.cpp
index d38aed08c0..2c77a13258 100644
--- a/src/neighbor.cpp
+++ b/src/neighbor.cpp
@@ -1941,6 +1941,7 @@ int Neighbor::decide()
    conservative shrink procedure:
      compute distance each of 8 corners of box has moved since last reneighbor
      reduce skin distance by sum of 2 largest of the 8 values
+     if reduced skin distance is negative, set to zero 
      new trigger = 1/2 of reduced skin distance
    for orthogonal box, only need 2 lo/hi corners
    for triclinic, need all 8 corners since deformations can displace all 8
@@ -1962,6 +1963,7 @@ int Neighbor::check_distance()
       delz = bboxhi[2] - boxhi_hold[2];
       delta2 = sqrt(delx*delx + dely*dely + delz*delz);
       delta = 0.5 * (skin - (delta1+delta2));
+      if (delta < 0.0) delta = 0.0; 
       deltasq = delta*delta;
     } else {
       domain->box_corners();
@@ -1975,6 +1977,7 @@ int Neighbor::check_distance()
         else if (delta > delta2) delta2 = delta;
       }
       delta = 0.5 * (skin - (delta1+delta2));
+      if (delta < 0.0) delta = 0.0; 
       deltasq = delta*delta;
     }
   } else deltasq = triggersq;