[Input] Include more significant digits for Redlich-Kwong coefficients

ctml_writer was severely truncating Redlich-Kwong coefficients when converting
from CTI to XML formats, keeping only 5 significant digints in the "a"
coefficients and two decimal digits in the "b" coefficients, which is less than
what is used even in the example CTI files. The use of the "%f" format also
meant that the precision depended on input units.

interfaces/cython/cantera/ctml_writer.py

@@ -845,11 +845,11 @@ class pureFluidParameters(activityCoefficients):
     def build(self,a):
         f= a.addChild("pureFluidParameters")
         f['species'] = self._species
-        s = '%10.4E, %10.4E \n' % (self._acoeff[0], self._acoeff[1])
+        s = '%.10g, %.10g\n' % (self._acoeff[0], self._acoeff[1])
         ac = f.addChild("a_coeff",s)
         ac["units"] = _upres+'-'+_ulen+'6/'+_umol+'2'
         ac["model"] = "linear_a"
-        s = '%0.2f \n' % self._bcoeff
+        s = '%.10g\n' % self._bcoeff
         bc = f.addChild("b_coeff",s)
         bc["units"] = _ulen+'3/'+_umol
 
@@ -864,12 +864,12 @@ class crossFluidParameters(activityCoefficients):
         f= a.addChild("crossFluidParameters")
         f["species2"] = self._species2
         f["species1"] = self._species1
-        s = '%10.4E, %10.4E \n' % (self._acoeff[0], self._acoeff[1])
+        s = '%.10g, %.10g\n' % (self._acoeff[0], self._acoeff[1])
         ac = f.addChild("a_coeff",s)
         ac["units"] = _upres+'-'+_ulen+'6/'+_umol+'2'
         ac["model"] = "linear_a"
         if self._bcoeff:
-            s = '%0.2f \n' % self._bcoeff
+            s = '%.10g\n' % self._bcoeff
             bc = f.addChild("b_coeff",s)
             bc["units"] = _ulen+'3/'+_umol
 

test/thermo/RedlichKwongMFTP_Test.cpp

@@ -38,15 +38,15 @@ TEST_F(RedlichKwongMFTP_Test, chem_potentials)
     // where gamma_k is the activity coefficient.  Run regression test against values calculated using
     // the model.
     const double expected_result[9] = {
-        -4.573578067074649e+008,
+        -4.573578072583122e+008,
-        -4.573471163377696e+008,
+        -4.573471168532005e+008,
-        -4.573375748803425e+008,
+        -4.573375753640399e+008,
-        -4.573290065058332e+008,
+        -4.573290069609340e+008,
-        -4.573212695326964e+008,
+        -4.573212699618942e+008,
-        -4.573142485189869e+008,
+        -4.573142489246118e+008,
-        -4.573078484551440e+008,
+        -4.573078488392255e+008,
-        -4.573019904340246e+008,
+        -4.573019907983406e+008,
-        -4.572966083775078e+008
+        -4.572966087236250e+008
     };
 
     double xmin = 0.6;
@@ -125,30 +125,30 @@ TEST_F(RedlichKwongMFTP_Test, setTP)
 
     // All sub-cooled liquid:
     const double p1[6] = {
-        1.587029921158317e+002,
+        1.587112190732014e+002,
-        1.541895558698696e+002,
+        1.541966713372675e+002,
-        1.501572815648243e+002,
+        1.501635359781652e+002,
-        1.465106359800041e+002,
+        1.465162036435630e+002,
-        1.431807662747959e+002,
+        1.431857735462774e+002,
-        1.401162435728261e+002
+        1.401207850479111e+002
     };
     // Phase change between temperatures 4 & 5:
     const double p2[6] = {
-        6.265136821574670e+002,
+        6.267097216456422e+002,
-        5.991027079853330e+002,
+        5.993217207540168e+002,
-        5.656903533839055e+002,
+        5.659501111117172e+002,
-        5.196021189855490e+002,
+        5.199644273242080e+002,
-        3.384435863009947e+002,
+        3.393007538579040e+002,
-        2.755331531855265e+002
+        2.756259035569044e+002
     };
     // Supercritical; no discontinuity in rho values:
     const double p3[6] = {
-        6.839819449357851e+002,
+        6.841288400828764e+002,
-        6.667277456641792e+002,
+        6.668789423328959e+002,
-        6.483568057147166e+002,
+        6.485130892980700e+002,
-        6.286479753170340e+002,
+        6.288103574172300e+002,
-        6.073051275696215e+002,
+        6.074749284756613e+002,
-        5.839223896051005e+002
+        5.841013398471708e+002
     };
 
     for(int i=0; i<6; ++i)