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•Calculate the Electron Affinity of Helium、Neon、Argon, by using B3LYP、MP2 and M062X theoretical methods with cc-pVTZ、aug-cc-pVTZ、d-aug-cc-pVTZ basis set, and do some simple statistical analysis.

excelQ1Q3， excelQ2

EA		MP2			EA		B3LYP			EA		M062X
(unit:kcal/mol)	Exp	cc-pVTZ	aug-cc-pVTZ	d-aug-cc-pVTZ	(unit:kcal/mol)	Exp	cc-pVTZ	aug-cc-pVTZ	d-aug-cc-pVTZ	(unit:kcal/mol)	Exp	cc-pVTZ	aug-cc-pVTZ	d-aug-cc-pVTZ
He	-5	-394.5	-68.3	-13.2	He	-5	-376.8	-61.9	-10.1	He	-5	-367.4	-62.7	-10.7
Ne	-6.9	-672.0	-141.3	-33.4	Ne	-6.9	-630.0	-130.2	-28.4	Ne	-6.9	-634.6	-131.7	-31.8
Ar	-8.4	-330.7	-77.8	-77.8	Ar	-8.4	-302.7	-72.2	-72.2	Ar	-8.4	-301.1	-72.8	-72.8

Reference : Atkins' PHYSICAL CHEMISTRY 10th Ed

• Conclusion : The bigger basis set we use, the higher level of accuracy achieved.

 

 

 

•Try to add an additional set of diffuse functions for the s orbital of He, and the s and p orbitals of Ne and Ar. ( in the 6-31G basis set )

 

• Conclusion : The bigger basis set we use, the higher level of accuracy achieved.

 

 

 

•Try to use Gaussian or WebMO to optimize the H₃⁺ molecule and calculate the linear dissociation energy according to the formula provided in the PDF lecture.

H³⁺ → 2H + H⁺

H³⁺ →H₂ + H⁺

H³⁺ → H₂⁺ + H

#CISD/aug-cc-pVTZ		unit:kcal/mol
H3+	H	H+	H2	H2+
-801.4	-313.6	0.0	-735.8	-378.0

H3+	2H, H+	H2, H+	H2+, H
-801.4	-627.3	-735.8	-691.6
dissociation energy	174.1	65.6	109.8