From b44f189569c92ed3646d87b737fb66ae61cf7a57 Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Fri, 9 Aug 2019 13:30:47 -0400
Subject: [PATCH] [Thermo] Avoid NaN in entropy with small negative mass
 fractions

Avoid NaN results in entropy_mole calculations when there are small negative
mass fractions. Consistent with the approach used elsewhere,
e.g. IdealGasPhase::getPartialMolarEntropies.
---
 src/thermo/Phase.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index a39cea996..85798d5ec 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -657,7 +657,7 @@ doublereal Phase::sum_xlogx() const
 {
     double sumxlogx = 0;
     for (size_t k = 0; k < m_kk; k++) {
-        sumxlogx += m_ym[k] * std::log(m_ym[k] + Tiny);
+        sumxlogx += m_ym[k] * std::log(std::max(m_ym[k], SmallNumber));
     }
     return m_mmw * sumxlogx + std::log(m_mmw);
 }