Comparison of CaF, ZnF, CaO, and ZnO: Their Anions and Cations in

Chapter 11

Comparison of CaF, ZnF, CaO, and ZnO: Their Anions and Cations in Their Ground and Low-Lying Excited States 1

2

Downloaded by NORTH CAROLINA STATE UNIV on September 14, 2012 | http://pubs.acs.org Publication Date: August 14, 2002 | doi: 10.1021/bk-2002-0828.ch011

J. F. Harrison , R. W. Field , and C . C. Jarrold

3

1

Department of Chemistry, Michigan State University, East Lansing, MI 48824-1322 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, M A 02139-4307 Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607-7061 2

3

Abstract The results of large basis set ab initio electronic structure calculations using the RCCSD(T) method are reported for the bond lengths, bond energies, excitation energies, vibrational frequencies, dipole moments and charge distributions for the titled molecules and where possible compared with experiment and previous calculations The striking differences between the Ca and Zn compounds are discussed in terms of their relative ionic character.

Introduction The excited electronic states of CaO and CaF may be understood in terms of a ligand field model (1,2) in which Ca is essentially C a and hosts a 4s, 4p or 3d electron which is perturbed by the companion anion. Since Ca and Zn are ostensibly similar, both having an outer 4s configuration, the question arises whether the excited states of ZnO and ZnF can be understood in terms of a similar ligand field model. Recent work on the photoelectron spectrum of ZnO and ZnF by Moravec et. al. (3) suggests that the answer is no and we will demonstrate that the reason is, primarily, because the Zn compounds are considerably less ionic than the corresponding Ca compounds. In this paper we compare and contrast the electronic structure of the title compounds. +

2

238

© 2002 American Chemical Society

In Low-Lying Potential Energy Surfaces; Hoffmann, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002.

239


Technical Details Unless otherwise noted, all calculations used the M O L P R O (4,5) system of programs (Versions 96.4 and higher) and the RCCSD(T) (6,7,8) method. The F and Ο basis sets were the A N O contraction of the Dunning aug-cc-pvqz set (9) with the g functions deleted (13s7p4d3f contracted to 6s5p4d3f). The Zn basis is from Heineman, Koch and Partridge(lO) and is a 20sl5p9d6f4g primitive set with an A N O contraction to 7s6p4d3f2g , while for Ca we use the basis of Bauschlicher, Rosi and Langhoff(ll), which is a primitive 20sl5p9d5£2g, contracted to 8s7p7d5£2g. Electron affinities, ionization energies and T 's are corrected for zero point vibration and scalar relativistic effects. The relativistic corrections and electron populations were obtained from a CISD calculation at the RCCSD(T) equilibrium geometry. A l l dissociation energies, D , are reported relative to the lowest energy neutral adiabatic asymptote appropriate to the molecular symmetry. For example, D for CaO(X E*) is relative to Ca( P) + 0( P) while for ZnO (Χ*Σ ) it is relative to Zn(*S) + 0 ( D ) . 0

0

l

3

3

0

+

1

Previous Theoretical Work Theoretical work on CaO dates from the early single configuration studies of Yoshimine (12), McLean and Yoshimine (13) and Carlson et. al. (14), all of which predicted the wrong ground state. Bauschlicher and Yarkony (15) pointed out the inadequacy of the single configuration representation of the Χ Σ state, while calculations by England (16) were the first to obtain Σ as the ground state, in agreement with experiment (17). England also noted that the bond lengths calculated without corevalence correlation were too long. In 1982 Diffenderfer and Yarkony (18,19) studied the low-lying X Z a n d Ή excited states while Bauschlicher and Partridge (20) corroborated the experimental dissociation energy of Irvin and Dagdigian (21) for the Χ Σ state. More recent work on CaF (22,23), CaO(24), C a O and C a F (25) will be discussed latter. Bauschlicher and Langhoff published (26) the first high-level calculation of ZnO and pointed out the sensitivity of the predicted ground state to the level of electron correlation. Subsequent work on ZnF(27,28), ZnO(28,29), and ZnO"(29,30) will be discussed latter. !

ι

+

+

1

+

1

+

+

+


240

Atomic Characteristics As one goes from Ca to Zn the 3d shell fills but does not completely shield the additional nuclear charge, resulting in the ionization energy (31) of Z n (9.39leV) being much larger than Ca (6.111eV). In addition, the atomic energy level pattern in Figure 1 shows that the P(4s4p) and the D (4s3d) states of Ca are 1.892 and 2.525eV above the ground state while in Zn the P(4s4p) is at 4.054eV and the 4d orbitals lie 7.7eV above the ground *S. These low lying atomic states in C a permit the atom to use pir and dir electrons in bonding, an option not energetically available to Zn. The situation in the positive ion is much more dramatic (31). The first excited state of C a is a D(3d) state at 1.697eV while the P(4p) is only 3.142eV above the Ca ( S). In contrast, the first excited state of Z n is a P(4p) state at 6.083eV. Clearly, Ca is a transition element in waiting! The proximity of the Ca 3d orbital to the ground state in both the neutral atom and positive ion plays a significant role in the electronic structure of CaF and CaO (vide infra). 3

3


3

+

2

+

2

2

+

2

Figure 7. Selected energy levels ofCa and Zn


241

CaF and ZnF Results Neutrals 2

+

Consider first the Χ Σ state of CaF and ZnF. The lowest neutral asymptote is the *S (metal) + P (F) and we envision a bond being formed between a sz hybrid on the metal (pointing toward the F) and the F 2p orbital with the unpaired electron in the SZ hybrid on the metal pointing 2

U


z

l

2

away from F. The valence electron configuration is sz (sz + / ? ) #

4

where

σ

the i i electrons are localized on F. In the ionic limit the σ bonding electron pair will be transferred to F resulting in the configuration sz ρ

σ

π .

The population analysis shown in Table 1 suggests that while both molecules are considerably ionic, CaF is more so. This is consistent with the lowest ionic asymptote in CaF being 2.7leV above the ground state products and the resulting ionic curve crossing this asymptote at 5.31Â (2.7 R ) while the ionic products in ZnF are 5.99eV above ground and cross at 2.40Â (1.4 Re). The calculated spectroscopic properties of CaF (Table 2) are in reasonable agreement with experiment and previous calculations. Our calculated ionization energy (Table 3) of CaF (5.82leV) is in good agreement with experiment (32)(5.828eV) and is approximately 0.3eV lower than the IP of Ca. Since the IP of CaF is equal to the Π of C a plus the difference between the D of the neutral and positive molecule, CaF ( Σ ) is more bound by approximately 0.3eV than CaF( E ) (vide infra). Similarly since the electron affinity of CaF (calc. 1.028eV) is equal to the E A of F(calc, 3.329eV ) plus the difference between the D of the anion and the neutral molecule, the neutral is bound by 2.3eV more than the anion. Note that because our calculated E A of F( P) is too small (33) by 0.072eV, a better estimate of the E A of CaF is our calculated value plus this differential, or 1.095eV. The molecular E A corrected for the error in the atom is shown in parenthesis in Table 3. The calculated IP of ZnF is 9.30eV, which is slightly smaller than our calculated IP of Zn (9.319eV, exp 9.39 leV) and so the bond energies in the neutral and positive ion are very similar. Our calculated E A of ZnF, corrected for the error in the E A of atomic F and for relativity (0.04SeV) is 1.929eV, somewhat smaller than the experimental (3) value of 1.974(8)eV. Our calculations imply that D of Z n F ( E ) is 1.435eV larger than Z n F ^ E ) in reasonable agreement with the experimental value of 1.427eV. e

5

+

1

+

0

2

+

0

2

0

2

+

4



0.07

0.20

0.21

0.18

-0.05

0.07

0.19

1.66

2.09

1.83

1.06

-0.03

0.22

ZnF( n )

CaF( Z )

ZnFfE*)

CaF( n )

ZnF( n )

3

3

!

2

r

r

+

r

r

0.08

-0.08

-0.03

CaF( n )

2

0.26

0.96

+

ZnF(X Z )

2

0.13

0.79

+

2

CaF(X Z )

σ

4ρ

4s

Molecule

0.03

-0.02

1.14

0.87

0.02

-0.02

1.14

0.38

0.02

0.02

TO

4p

0.03

-0.02

0.02

-0.02

0.02

-0.02

0.02

0.38

0.02

0.02

4.0

0.14

4.0

0.12

4.0

0.11

4.0

0.11

4.0

0.11

3cU

0.07 2.0

2.0

2.0

0.04

2.0

0.07

2.0

0.15

2.0

0.04

2.0

2.0 0.04

0.01

0.05

0.27

2.0

0.01

2.0

0.01

2.0

0.01

2.0

2.0

2.0

2.0

5+

0.01

3d

0.06

3cL

0.06

3d*

1.98

2.03

1.93

2.02

1.87

2.04

1.98

2.03

1.97

2.02

2s σ

1.72

1.89

1.81

1.93

1.80

1.95

1.75

1.92

1.80

1.93

2ρ

Table 1. Fluoride Population Analysis Pny

1.91 1.94

1.94

1.97

1.95

1.98

1.96

1.91

1.84

1.96

1.98

1.96

1.95

1.93

1.94 1.85

1.96

1.94

2

1.96

1.94

2pn;

+1.62

+1.79

-0.43

-0.11

-0.36

-0.07

+0.55

+0.86

+0.72

+0.86

-0.62

-0.79

-0.57

-0.89

-0.64

-0.93

-0.55

-0.86

-0.72

-0.86

Q(M) Q(F)



243

Table 2. Fluoride results, previous calculations and experiment Molecule

Source

Re(Â)

CàFÇft?)

This work 1.957 Previous 1.966 Experiment 1.967 This work 1.775 Previous 1.796 Previous 1.787 Experiment This work 1.943 Experiment 1.952 This work 1.757 Experiment This work 2.018 This work 1.913 Experiment Χ Σ +0.15 1.992 This work This work 1.826 This work 1.876 Previous 1.881 This work 1.708 22

38

2

ZnFCX !^

28

27

3

2

CaF( n ) r

38

2

ZnF( n ) r

29

CaFXX'Z*) ZnFCX'E ) 1

3

3

CaF( n ) ZnF( n ) CaF'C'Z*) r

3

r

25

ΖηΤ^'Σ*)

l

2

3

2

2

+

1

CueCcm") D (eV)

T (eV)

587 583 581 633 593 601 620(10) 594 587 659 630 509 425 420(10) 537 541 692 756 748

0.0 0.0 0.0 0.0 0.0 0.0

0

38

5.47" 5.51° 5.55* ' 3.12"

39 40

1.99" 5.30* 5.40* 2.59* 3.17 1.60

e

e

4.04* 3.19* 5.80 5.67 3.15 e

e

e

0

2.05 2.044 4.63 4.586 0.0 0.0 0.0 1.08 2.53 0.0 0.0 0.0

a. Relative to M( S) + F( P) b. Relative to M( P) + F( P) c. Relative to M ^ S ) + F(*S) d. Relative to M( P) + F ( S ) e. Relative to M ( S ) + F( P) 3

+

2

!

2


244 2

The first excited state of CaF and ZnF is Α Π with the configuration Γ

2

4

^ (sz + ρ ) π m

where the singly occupied it electron is localized on the

σ

m

3

2

metal. The lowest energy asymptote is P (metal) + P (F), which is 1.86eV and 3.966eV above the ground state products in CaF and ZnF. In U

2

U

A

the ionic limit the configuration is n p n m

2

and the lowest Π ionic Γ


2

asymptote has the metal ion in a P state. The ionic curves will cross the neutral asymptote at 5.65À (2.9 Re) in CaF and 1.78À (1.0 Re) in ZnF and accordingly we expect CaF to be significantly more ionic than ZnF and this is supported by the population analysis (Table 1). 10

21

The singly occupied 7r in CaF has the composition p^ d^ m

l

while in

+2

ZnF it is p f. Given that the energy of the 3d orbital in C a D(3d) is 1.697 2

2

eV above the S(4s), while the P(4p) is 3.142eV, it is surprising, in so ionic a molecule, that the 3d orbital is not dominant. It could be that this composition is energetically favored over a single d electron because of the increased polarizability of the 4p component, the reduced repulsion with the F IT orbitals that obtains when the p d orbital hybridizes away from F , and n

n

the more favorable quadrupolar interaction with F(the zz component of the quadrupole tensor of the 4pir orbital is positive while that of the du is negative). As first noted by Ernst and Kandler (35) this ρ ά π

π

mixing

2

explains why the dipole moment of CaF (Table 4) in the Α Π state (2.57D cale, 2.44D experiment) is significantly smaller than that of ZnF while in the ground state they are comparable (3.05D vs. experiment (36), 3.12D). Note that, for ZnF, the Α Π state is stabilized by the quadrupolar interaction of the metal centered ρ orbital with F". The bond length of both CaF and ZnF in the excited Α Π state is smaller than in the ground Χ Σ , state, contracting by 0.014 and 0.018Â, while the corresponding frequencies increase by 7 and 26 cm" respectively. The generalized Morse potentials (37) in which the molecules dissociate to their lowest neutral asymptotes, are shown in Figures 2 and 3 and illustrate the significantly larger D of CaF (an ionic effect) and the significantly smaller T which is a consequence of the much smaller *S, P separation in Ca relative to Zn. This small separation also permits the Α Π state in CaF to be bound relative to the ground state atoms . Γ

2

Γ

π

2

2

+

Γ

1

0

3

0

2

Γ

Anions Adding an electron to the singly occupied metal centered σ orbital in either the Χ Σ state, or Α Π state results in a state in which the additional 2

+

2

Γ


245

Table 3. Ionization Energies and Electron Affinities


Molecule

IP(eV) Calculated 6.767 9.260 5.821 9.303

CaOC'E") ΖηΟ^Σ*) CaF( E ) ZnF( 5T) 2

+

2

EA(eV) Experiment 6.66(8) 42

5.828

36

Calculated 0.865(0.977) 1.927(2.039) 1.028(1.095) 1.857(1.929)

Experiment 3 34

2.087 '

1.974(8)

3 1

Ca('S)

6.097

6. I l l

Zn('S)

9.319

9.391

31

F( P)

2

3.329

3.401

3

1.349

1.461

0( P)

Table 4. Dipole moments (Debye) Molecule

This Work

Experiment

CaFiX^*)

3.05

3.07(7)

2

+

36

Previous Calculation

3.06 3.24

28

8.84

8.64

16

5.49

5.37

28

CaO( nO

3.48

3.39

16

ZnOOTIi)

2.62

2.61

28

2.61

2.55

16

ZnF(X Z ) 2

CaF( n )

2.57

r

2

ZnF( n ) +

ι

ΖηΟ(Χ Σ*)

4

CaOÊ ) 3

4

ZnCK ! )

2.44

35

3.80

r

CaO(X'Z ) 3

3.12

3.11

28

3.12 /3.09

:


33

33

3

246 +

3

electron is localized on the metal (see Table 1). In the *Z and Π states of CaF' and ZnF", F has a Mulliken charge very similar to its charge in the neutral predecessors. There are no previous calculations on these molecules and the only experimental (3) data is the bond length of ZnF' (Χ Σ ) relative to ZnF Γ


ι

+

R ( Angstroms)

Figure 2. Generalized Morse Potentials for CaF and CaF

R (Angstroms)

Figure 3. Generalized Morse Potentials for ZnF and ZnF

2

(Χ Σ*). Our calculated differential is +0.138Â, in reasonable agreement with the experimental value of +0.150Â. The bond length contraction upon


247 excitation discussed earlier for the neutral fluorides is also seen in the anions. In CaF" the Π bond length is 0.02Â shorter than in the Χ Σ state while in ZnF" the contraction is a substantial 0.087Â. The Morse potential curves shown in Figures 2 and 3 illustrate several interesting features. The Π state of C a F and the Σ state of CaF are both bound relative to the Ca^S) + F ( S ) asymptote while neither ZnF( E ) nor Z n F ( n ) are bound relative to Zn ( S) + F ( S ) . As noted, the small C a ^ S , P) separation of 1.86eV (less than the electron affinity of F) plays a major role in this. Also, the C a F ( n ) state is 0.03eV below the CaF( X ) state while ZnF"( n ) is 0.60eV above the ZnF( E ). These energy separations at the equilibrium geometry for each state are summarized in Figure 4. 3

ι

+

Γ

3

2

+

Γ

!

3

2

l

+

l

r


3

3

2

+

r

3

2

+

r

2

ZnF ( n ;4.63ev) r

3

2

CaF' ( n ; ~0.03eV)

+

ZnF ( Σ ; 0.0 eV)

r

CaF' (V; -1.1 OeV) -

ZnF (V;-1.93eV)

Figure 4. Comparison of CaF and ZnF and their Anions

Cations 2

+

Removing an electron in the singly occupied σ orbital from the Χ Σ state of either ZnF or CaF results in a Χ Σ state. The population analysis in !

+


248 Table 1 supports the view that the removed electron comes from the metal, as the Mulliken charge on F is only slightly less negative than in the neutral molecule. Clearly the large electrostatic stabilization that results from the highly positive metal and the negative F makes electron transfer to the metal energetically unfavorable. In both cations the calculated D is larger than that of the neutral parent, another reflection of the increased ionic character. There are no experimental data on these cations . While our D and Rg for CaF*" are in reasonable agreement with the previous calculations of Partridge et al (25), our vibration frequency is significantly smaller. 0


0

CaO and ZnO Results Neutrals +

While both CaO and ZnO have a Χ*Σ ground state they dissociate to different atomic electronic states. The lowest neutral asymptote for CaO has Ca in an excited P and Ο in the ground P . This asymptote permits a sigma bond between the Ca 4s and Ο 2pz orbitals (taking the internuclear line as the ζ axis) and a it bond that is a mixture of a covalent interaction between the Ca itx orbital and the Ο px and a dative bond involving donation from the Ο py lone pair into the formally empty Ca ity orbital. The proximity of the P and D states of Ca ensures significant 3d character in the Ca IT orbital. The lowest ionic asymptote (Ca 0~) permits a sigma bond between the C a 4s and the O" 2pz orbitals, and two dative bonds from the Ο lone pairs in the it system. The low-lying pit and dit orbitals on C a facilitate significant back donation. This ionic curve will cross the neutral asymptote around 5.16Â, which is 2.8 times Re (vide infra) while the doubly ionic asymptote (CaÔ") will cross the neutral asymptote around 3.9A (2.1 R ) . The early crossing of these two ionic curves with the neutral asymptote insures that the Χ*Σ state will have considerable ionic character. The lowest neutral asymptote for ZnO has Z n in the ground *S and Ο in the excited D state. This asymptote permits a dative sigma bond between the Zn 4s pair and the empty Ο pz. Both ionic asymptotes (Zn 0" and Z n ^ O " ) cross the neutral asymptote at 2.41Â or 1.4 R and accordingly one expects less ionic character than in CaO. The lowest ionic asymptote permits a covalent bond between the singly occupied 4s and 2p on Z n and O" and the same dative bonds as in Ca 0", however, since the pTt orbital in Z n lies at much higher energy than the dit orbitals in C a they are not expected to participate as fully. The population analysis in Table 5 suggests that CaO be viewed as C a ^ O " with considerable back-donation from Ο to the Ca 3d orbitals, resulting in a 3d population of 0.77 electrons. ZnO however does appear to be consistent with a single bond between Zn (4s) and Ο" (2ρ ). 3

3

U

g

3

3

U

+

+

+

e

+

l

g

+

e

+

z

+

+

+

+

σ



0.16

0.29

0.78

1.04

r

-0.01

0.07

0.08

-0.06

0.07

0.39

-0.05

0.16

ΖηΟ ( Πί)

CaO^Z*)

ΖηΟ ( Σ+)

+ 2

+ 2

+ 2

-0.05

-0.03

CaO ( n.)

0.01

-0.02

1.28

0.07

0.90

Γ

Ζηθχ Π )

2

-0.04

0.67

0.01

-0.02

0.11

0.03

0.04

-0.02

0.01

-0.01

0.09

0.02

ro

4p

0.0

CaO( n )

2

0.24

2.17

Ζηθχ Πΐ)

2

0.18

1.77

CaO( ni)

2

0.43

1.17

ΖηΟ( Σ )

+

2

0.28

0.71

CaO( E )

+

0.91

ΖηΟ^Σ*)

2

0.27

0.75

0.14

0.05

CaO^Z )

4

ΖηΟ( Πΐ)

3

CaO( ni)

3

0.95

ΖηΟζΧ'Σ*)

-0.04

0.01

1

σ

CaOCX !*)

4ρ

4s

Molecule

0.07

4.0

0.10

4.0

0.05 -0.01

0.17

4.0

0.26

4.0

0.13

4.0

0.24

4.0

0.08

4.0

0.13

2.0

0.12

2.0

0.03

2.0

0.48

2.0

0.02

2.0

0.19

2.0

0.08

2.0

0.03

2.0

4.0

3d*, 0.23

0+5

0.31

3d

-0.01

0.08

0.02

0.03

-0.01

0.11

0.03

0.04

-0.02

0.04

-0.04

0.09

0.02

4ρ»η

2.0

0.12

2.0

0.10

2.0

0.21

2.0

0.05

2.0

0.19

2.0

0.08

2.0

0.07

2.0

0.23

3d, 5+

2.0

0.01

2.0

0.01

2.0

0.01

2.0

0.02

2.0

0.01

2.0

0.01

2.0

0.01

2.0

0.01

3d

1.90

2.02

1.95

2.04

1.90

2.03

1.83

2.00

1.92

2.00

1.92

2.03

1.94

2.03

1.90

2.03

2s σ

0.98 1.86 1.90

0.96 0.86

0.97

1.70

1.81

0.99

0.99

1.87

1.75

1.93

1.90

0.99

0.98

1.88

1.72

œ

2p

1.55

1.84

1.16

1.73

1.73

1.88

1.48

1.77

0.91

0.98

1.70

1.89

1.11

1.67

2ρ

Table 5.0xide Population Analysis Pîty

1.90

1.86

1.92

1.87

1.90

1.74

1.96

1.93

1.87

1.75

1.93

1.90

1.94

1.91

1.88

1.72

2


-0.68

-1.35

-0.53

-0.84

-1.17

-1.32

-0.72

-0.85

-0.61

-0.85

-0.82

-1.18

-0.45

+ 1.60 -0.60

+ 1.75 -0.75

+1.45

+ 1.77 -0.77

-0.32

+0.35

-0.47

-0.16

+0.17

+0.32

+0.72

+0.85

+0.61

+0.85

+0.82

+ 1.18

Q(M) Q(X)

vo

250

Calculated and experimental spectroscopic properties of the neutral oxides are collected in Table 6 The a ni state of both molecules correlate to the lowest atomic asymptotes, which permits a sigma bond between the singly occupied Ο 2p orbital and an sz hybrid on the metal, leaving the triplet coupled electrons in the companion sz hybrid on the metal and on Ο in the pir orbital. Note that only a singly charged ionic asymptote can contribute to this state (and the Σ , vide infra) and the lowest ionic crossings occur at 3.10Â (2.1 Re) and 1.8Â (1.0 Re) for CaO and ZnO respectively, consistent with the population analysis results (Table 5) that CaO is the more ionic. The Σ states of both molecules correlate to the excited P state of the metal and the ground P state of O. The four unpaired electrons in this asymptote can be triplet coupled in three ways and this permits the wave function to be a mixture of a σ bond with the IT electrons triplet coupled and a Έ bond with the σ electrons triplet coupled. The lowest ionic asymptote, metal (4s) + 0"(2p ) has the -κ electrons singlet coupled and crosses the neutral asymptotes at 5.16À (2.6 Re, Ca 0") and 3.66Â (2.0 R , Z n 0 " ) suggesting that the triplet coupled electrons will be primarily in the σ system. Because the S - D separation in C a is only 1.697 eV, a second ionic asymptote, Ca ( D) + 0"( P) is important and crosses at 3.21 A (1.6 Re), differentially stabilizing CaO, over ZnO. The relative locations of these states are shown in Figures 5 and 6. 3

z


3

+

3

+

3

U

3

g

5

+

+

e

2

+

J

2

2

ι

0

+

2

I

2

ι

>

4

ι

I

6

ι

I

8

R(AngBtnorrB)

Figure 5. Generalized Morse Potentials for CaO


251

Table 6. Oxide results, previous calculations and experiment


Molecule

+

CaO(X'E )

4

ΖηΟίΧ'Σ )

Re(Â)

ci^cm" )

D (eV)

T (eV)

This work Previous Experiment This work Previous Previous Experiment Experiment

1.829 1.886 1.8221 1.715 1.719 1.733

721 677 732 741 727 690 805(40) 720(20)

5.91" 6.03"· 5.96"· 3.54* 3.59* 3.25* 3.57

0.0 0.0 0.0 0.0 0.0 0.0

16

29

28

CaOC'nO

1

Source

16

3

This work 2.082 Previous 2.086 Previous 2.153 Experiment 2.099 This work 1.850 Previous 1.857 Previous 1.873 Experiment Χ'Σ +0.126 24

16

17

3

ΖηΟ( Πί)

29

28

+

CaOÊ*)

This work 1.964 Previous 2.031 This work 1.801 Previous 1.818 Previous 1.816 Experiment X^ +0.086 16

ΖηΟ^Σ*)

28

38

3

3

+

3

543 544 508 556 577 567 525 550(20) 587 554 596 561 611 560(20)

34

0

41

21

M2

3.07 3.08

c

0.92

c

1.36 '

1.031 0.35 0.26 0.04 0.313(10)

4.78°

1.07

1.31 1.38

c

c

3

0

c 34

3.87

d

1.83 1.512 1.465 1.875(10)

3

a. Relative to Ca( P) + 0( P) b. Relative to Zn( S)+ 0 ^ 0 ) c. Relative to ground state products d. Relative to Zn( P) + 0( P) !

3

3


3

252 50000

40000


30000

1

1

• 2

Comparison of CaF, ZnF, CaO, and ZnO: Their Anions and Cations in

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