From 008f2ec2204e1cf2339121e26413e423a981190b Mon Sep 17 00:00:00 2001
From: Jon Walsh <jonathan.a.walsh@gmail.com>
Date: Tue, 4 Apr 2017 07:46:39 -0700
Subject: [PATCH] disallow negative resonance scattering energy bounds

---
 src/physics.F90 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/physics.F90 b/src/physics.F90
index df7ffd679..913533da8 100644
--- a/src/physics.F90
+++ b/src/physics.F90
@@ -875,9 +875,9 @@ contains
       wgt = wcf * wgt
 
     case (RES_SCAT_DBRC, RES_SCAT_ARES)
-      E_red = sqrt((awr * E) / kT)
-      E_low = (((E_red - FOUR)**2) * kT) / awr
-      E_up  = (((E_red + FOUR)**2) * kT) / awr
+      E_red = sqrt(awr * E / kT)
+      E_low = max(ZERO, E_red - FOUR)**2 * kT / awr
+      E_up  = (E_red + FOUR)**2 * kT / awr
 
       ! find lower and upper energy bound indices
       ! lower index