KCN
		Nitrogen and Potassium
	Nuclear Quadrupole Coupling Constants
		in Potassium Cyanide
	"Gaseous alkali metal cyanides are floppy molecules." [1].  Thus, the nqcc's measured in the ground rotational state, but with large amplitude vibrational motion, and the nqcc's calculated on a rigid molecular structure cannot be expected to agree very well.  Nevertheless, we have undertaken calculation of the nitrogen and potassium nqcc's in KCN on both substitution and effective structures derived by van Vaals et al. [1].  The results for nitrogen are compared with the experimental nqcc's in Tables 1 and 2.  Calculated and experimental potassium nqcc's are compared in Tables 3 and 4. Structure parameters are given  in Table 5.
	Table 1. Nitrogen nqcc's in KCN (MHz).     Calculation was made on the substitution structure.   Calc. Expt. [1]     14N Xaa 2.024 1.921(4) Xbb - 4.101 - 4.041(15)   Xcc 2.077 2.120 * |Xab| 0.960   RMS 0.073 (2.7 %)   RSD 0.030 (1.3 %)   Xxx 2.171 1.995(23) Xyy 2.077 2.120 Xzz - 4.248 - 4.110(25) ETA - 0.022 0.029(13)  Øz,a 81.29 83.7(10)  Øa,CN 81.25  Øz,CN   0.04
	* Calculated here from zero trace condition.
	Table 2. Nitrogen nqcc's in KCN (MHz).     Calculation was made on the effective structure.   Calc. Expt. [1]     14N Xaa 2.078 1.921(4) Xbb - 4.169 - 4.041(15)   Xcc 2.091 2.120 * |Xab| 0.891   RMS 0.118 (4.4 %)   RSD 0.030 (1.3 %)   Xxx 2.202 1.995(23) Xyy 2.091 2.120 Xzz - 4.294 - 4.110(25) ETA - 0.026 0.029(13)  Øz,a 82.04 83.7(10)  Øa,CN 81.88  Øz,CN   0.16   1.8(10)
	Table 3. Potassium nqcc's in KCN (MHz).     Calculation was made on the substitution structure.   Calc. Expt. [1]     39K Xaa - 5.570 - 5.605(5) Xbb 2.595 2.594(11)   Xcc 2.975 3.011 * |Xab| 0.396   RMS 0.029 (0.78 %)   RSD 0.026 (0.60 %)   Xxx 2.614 2.637(9) Xyy 2.975 3.011 Xzz - 5.589 - 5.645(10) ETA 0.064 0.066  Øz,a   2.77   4.0(7)  Øa,CN 81.25  Øz,CN 84.02
	Table 4. Potassium nqcc's in KCN (MHz).     Calculation was made on the effective structure.   Calc. Expt. [1]     39K Xaa - 5.467 - 5.605(5) Xbb 2.540 2.594(11)   Xcc 2.927 3.011 * |Xab| 0.350   RMS 0.062 (1.6 %)   RSD 0.026 (0.60 %)   Xxx 2.555 2.637(9) Xyy 2.927 3.011 Xzz - 5.482 - 5.645(10) ETA 0.068 0.066  Øz,a   2.50   4.0(7)  Øa,CN 81.88  Øz,CN 84.38 85.9(7)
	Table 4. Molecular Structures [1].  T - Shaped   rs  (Å) ro  (Å) CN 1.174(2) 1.169(3) KC 2.711(5) 2.716(9) KN 2.532(5) 2.549(9)
	[1] J.J.vanVaals, W.LeoMeerts, and A.Dymanus, J.Mol.Spectrosc. 106,280(1984).
	CN Anion		NaCN		LiNC
	Table of Contents
	Molecules/Nitrogen
	Molecules/Potassium
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						Last Modified 3 Sept 2004