Electronic property

Electronic properties of any material depend on its electronic band structure (possible electronic energy levels). The band structure, and hence the electronic properties of CNTs, depend strongly on the diameter and chirality of the tube. There are numerous studies concerning the band structure of ideal CNTs as a function of these parameters [35,101-104]. Since CNTs may be considered a seamless cylinder formed by rolling a graphene sheet, it is worthwhile to study the graphene sheet structme to imderstand the band structure of CNTs. 

Graphene, a 2D array of carbon atoms, is a hexagonal arrangement of carbon atoms in which each sp hybridized carbon atom is bonded with three neighboring carbon atoms. The unhybridized p electrons form an electron cloud at both sides of the graphene plane. This electron cloud gives graphene its unique electronic properties. 

The 2D energy dispersion relation (E ) for a graphene sheet derived by using the tight binding approximation is given by [103,105]  

Band structure of CNTs may be derived from the graphene wave function along with the periodic boundary condition given by Equation 4.11. 

The wave vector turns out to be discrete along the circumferential direction, while along the tube axis, it remains unrestricted [102,103]. Since the tubes with different chirality have different band structure, their electronic properties are also different. 

Electronic properties of nanocrystals critically depend on size. This aspect is aptly put forth in the quest How many atoms make a metal . It is clear that as the size of metal nanocrystals is reduced, the accompanjung changes in the electronic structure render them insulating. This transition, called the size-induced metal-insulator transition (SIMIT), has evoked much interest from chemists and physicists alike. A SIMIT is manifested in experiments that measure the electronic band structure and atomistic properties such as ionization energy. 

4d states have little intensity at E. With the increasing particle size, new states emerge closer to Ef making the spectrum closer to that of the bulk metal. Similarly, the BI spectra of Ag nanoparticles showed a distinct feature which moves toward E with increasing size of the particles, accompanied by an increase in the intensity of the 5s band. Thus, both UP and BI spectra reveal that the density of states around E is depleted in the case of small particles and that the large nanocrystals effectively mimic the metallic state of the bulk. A SIMIT is indeed implied by these measurements. 

There have been attempts to design circuits that involve both self-assembly and exhibit single electron transport at room temperature [62-64]. It is possible to observe Coulomb blockade from Au nanocrystals linked to thiol molecules tethered to a Au surface [677]. Andres and coworkers [680] investigated 

Electrical transport measurements on layer-by-layer assemblies of nanocrystals on conducting substrates have been carried out with a sandwich configuration [691-693]. Nanocrystalline films with bulk metallic conductivity have been realized with Au nanocrystals of 5 and llnm diameter spaced with ionic and covalent spacers [692, 693]. The conductivity of monolayered two-dimensional arrays of metal nanocrystals has been examined with patterned electrodes [694-699], Structural disorder and interparticle separation distance are found to be key factors that determine the conductivity of such layers [694-697]. The conductivity of the layers can be enhanced by replacing the alkane thiol with an aromatic thiol in situ [698,699]. The interaction energy of nanocrystals in such organizations can be continually varied by changing the interparticle distance. 

The wavefunctions of the electronic states are the solutions to Schrodinger s equation. 

The strong scattering causes a large uncertainty in the electron momentum, through the uncertainty principle, 

The loss of /r-conservation is one of the most important results of disorder and changes much of the basic description of the electronic states. There is a greater emphasis on the spatial location of the carrier than on its momentum. Some consequences of the loss of k-conservation are  

Switendick was the first to apply modern electronic band theory to metal hydrides [5], He compared the measured density of electronic states with theoretical results derived from energy band calculations in binary and pseudo-binary systems. Recently, the band structures of intermetallic hydrides including LaNijH and FeTiH have been summarized in a review article by Gupta and Schlapbach [6], All exhibit certain common features upon the absorption of hydrogen and formation of a distinet hydride phase. They are  

The structural model for the DNA-templated aggregates indicates that two types of electronic coupling should be present. First, the face-to-face stacking of dye monomers to form a dimer will lead to splitting of the excited state (primary splitting). Then, for extended aggregates, end-to-end interactions between adjacent 

Primary Splitting Primary Splitting Primary Coupling 

FIGURE 7.9 Representation of electronic couplings associated with cyanine dye aggregation on DNA. Face-to-face stacking within a dimer leads to primary splitting, observed as a blue-shift in the absorption spectrum. End-to-end interactions between dimers yield secondary splittings of the blue-shifted band. 

Effect of Cyanine Dye Structure on Primary and Secondary Splittings in H-Aggregates 

To the extent that the electronic structure is describable in terms of independent atoms, the properties of inert-gas solids are easily understandable and not so interesting. There are, however, one or two points that should be made. The optical absorption spectra of isolated atoms consists of sharp lines that correspond to transitions of the atom to excited slates, and to a continuous spectrum of absorption beginning at the ionization energy and continuing to higher energy. The experimental absorption spectra of inert-gas solids (Baldini, 1962) also show fairly sharp lines corresponding to transitions from the valence p states to excited s 

The spectra may also be described in the language of solid state theory. The atomic excited states are the same as the excitons that were described, for semiconductors, at the close of Chapter 6. They are electrons in the conduction band that are bound to the valence-band hole thus they form an excitation that cannot carry current. The difference between atomic excited states and excitons is merely that of different extremes the weakly bound exciton found in the semiconductor is frequently called a Mott-Wannier exciton-, the tightly bound cxciton found in the inert-gas solid is called a Frenkel exciton. The important point is that thecxcitonic absorption that is so prominent in the spectra for inert-gas solids does not produce free carriers and therefore it docs not give a measure of the band gap but of a smaller energy. Values for the exciton energy are given in Table 12-4. 

One measure of the gap is the resonant energy listed in Table 12-4, which is seen to be slightly less than the free-atom ionization energy. Pantelides (1975c) noted 

The valence p state of an Inert-gas atom, viewed as a wave having a wavelength equal to the atomic diameter. 

Pantclides (1975c) also discussed the valence bands for the inert-gas solids, indicating that they consist of a narrow p band and an s band, which may be taken as completely sharp. He gave a universal width for the p band, of fi / md), with f/v = 4.2. (Again, his numerical value was different because of a different definition of d.) Presumably the conduction bands, corresponding to electrons added to the crystal, would be quite like free-electron bands. 

The solubility of a polymer will be altered by threading of the cyclic to form a polyrotaxane. The change is related to the properties and structures of both components. 

The aqueous solubility of CD also enables their potential application as poly-rotaxane-based drug carriers. Yui and coworkers incorporated CD onto PEO chains in polypseudorotaxanes and polyrotaxanes [92-94], The releasing kinetics of CD from the polymer chain were studied. The release was governed by the inclusion complexation equilibrium. Biodegradation to cleave the BG units was shown to cause the release of the CD from the polyrotaxanes. 

Lipatova and coworkers reported that cyclic urethane-based polystyrene rotax-ane) 26 was not soluble in benzene and DMSO whereas polystyrene itself is soluble [64-66]. This is probably because of the introduction of strong intermolecular hydrogen bonding between die cyclic urethane units in the crystalline domains. 

Gong et al. reported that the solubility of a polymeric cyclic can be altered significantly by threading with paraquat, the formation of 84 [126, 128]. Whereas polymer 83 was only partially soluble in acetone, polyrotaxanes 84 were soluble and had an orange color. Whereas polymer 83 was totally soluble in THF and paraquat was not soluble, 84 even up to min=0.971 were initially soluble except for a small amount of uncomplexed paraquat the solubility of paraquat was indeed enhanced by complexation with polymer 83. CH3CN was a good solvent for paraquat but poor for 83. However, all polyrotaxanes 84 with m n 0.428 were soluble, whereas 84 with m/n =0.232 was not this means that a certain amount of paraquat incorporation is necessary for 83 to be soluble. 

Therefore, die polarity and solubility of polymer can be modified deliberately by varying the nature of the components. High aqueous solubilities of polyamides and polyurethane threaded with crown ethers or CD are intriguing, because this observation implies potential applications of the polyrotaxane concept in coatings, adhesives, and water-borne processing. The observation of the emulsification of 

Hammett, who is arguably the father of physical organic chemistry, proposed that the ionisation of benzoic acids could be used as a chemical model system to characterise the electronic properties of different substituents. In the Hammett equation (eqn (8.1)), the reaction is characterised by a reaction constant, p, which quantifies the sensitivity of that particular reaction to the electronic effect of the substituent, which itself is described by a substituent constant, a  

In this equation, Kx is the equilibrium (or rate) constant for a process involving an X-substituted compound, and Kh is the corresponding constant for the unsubstituted parent. Hammett chose the ionisation of benzoic acids as a reference system and assigned a value of 1 as the reaction constant for this series. Substituent a values were then computed from measured pKa values of substituted benzoic acids, and quite extensive lists of a values have been compiled. One feature of this approach to the modelling of electronic effects is 

Several systematic experimental and computational studies have compared the sigma-donating abilities of NHCs and tertiary phosphines for a variety of transition-metal complexes [8-17]. As illustrative examples, analyses of the nickel-carbonyl complex 1 and iridium carbonyl complex 2 (Fig. 1) re- 

A detailed description of atomic and molecular theory is provided in texts by Figgis (1966), Cotton and Wilkinson (1988) and Atkins (1990). Here a brief summary of concepts and terms most relevant to the iron oxides is given. 

A partly filled shel exhibits a number of states of different energies which arise as a result of the interactions or couplings of the electrons in the shell. These states can be determined using the Russell-Saunders coupling scheme (Hund s rules) (Figgis, 1966). A characteristic property of a state is the spin multiplicity which is related to the number of unpaired electrons in a shell. A singlet state has a spin multiplicity of one (two electrons of opposite spin), a doublet state has a multiplicity of two and 

1) Electron spin strongly influences the magnetic properties of a compound. 

2) A shell is a set of orbitals with the same principal quantum number. 

The Iron Oxides Structure, Properties, Reactions, Occurences and Uses. R. M. Cornell, U. Schwertmann Copyright 2003 WILEY-VCH Verlag GmbH Co. KGaA.Weinheim ISBN 3-527-30274-3 

To determine the valence band offset at the interface, the binding energies of the core levels are plotted in dependence on deposition time in Fig. 4.30. Core 

According to our experience, it is more difficult to determine a reliable valence band offset for the Cu(In,Ga)Se2/ZnO interface than for the CdS/ZnO interface. This is related to the lower substrate core-level intensities because of the presence of multiple cations. The substrate intensity might, therefore, be already completely suppressed when the Zn 2p and the O Is derived valence band maxima (see filled circles and squares in Fig. 4.30) reach the same value, and, therefore, reflect a proper ZnO valence band maximum (end of the amorphous nucleation layer). This difficulty is not present in the data set in Fig. 4.30 and for a deposition time of 64 s a valence band offset of A/ y vis = 2.15 0.1 eV can be determined. In another experiment, we have derived a slightly smaller valence band offset of AEyb = 1.98 0.2 eV [70]. The larger uncertainty is due to the above-mentioned difficulties. 

The valence band offsets determined in our group are very close to values reported in literature. Platzer-Bjorkman et al. have determined A/ A is = 2.2 0.2 eV for ALD10-ZnO deposited onto CuInSe2 or Cu(In,Ga)Se2 [143, 144]. Weinhardt et al. give a valence band offset for ILGAR11-ZnO on CuIn(S,Se)2 substrates of A Vb = 1.8 0.2eV [60]. The comparable values for the different interface preparation and substrate compositions suggest a rather small variation of the band alignment with these parameters. 

1 Cu(In,Ga)Se2 Solar Cells with Iri2S3 Buffer Layers 

I112S3 or I112S3 containing compounds are possible alternatives for the CdS buffer layer in Cu(In,Ga)Se2 thin-film solar cells [120,145-148], The In2S3 layers are prepared by various techniques as chemical bath deposition [145], thermal evaporation [146], atomic layer deposition (ALD) [147], and magnetron sputtering [148], Energy conversion efficiencies above 16% have been 

As mentioned in Section 15.3.2, small gold particles give more active catalysts, but the decrease in size is accompanied by several other changes that are examined below. 

Decreasing the particle size leads to an increasing proportion of low coordinated surface atoms, such as edge and corner atoms. The presence of these sites is a key factor for catalytic activily, since they are required at least for the adsorption of CO, and possibly for that of O2 (see Section 15.4.3). 

The changes in the electronic properties and in the structure of the gold particles can also be reflected by changes in the Au Au bond distance. When supported metal particles are smaller than 3—4run, there is a contraction of the metal-metal 

The energy quantum used in NMR is much smaller than that needed for electron spectroscopy,but the response is less sensitive, and a large sample is needed also the interpretation is even less straightforward. Supported metal catalysts are very suitable for study and the Pt nucleus has been extensively examined (Section 2.4.2). This dependence of NMR amplitude on field/frequency shows separate, if not well resolved, peaks at 1.138 and 1.10 G kHz, corresponding respectively to Knight shifts of-3.34 and zero percent and thus to bulk and surface atoms. The plots have been imaginatively deconvoluted, but no use 

There have been a number of studies on the particle size dependence of ferromagnetic behaviour, but fewer on paramagnetic. Small palladium particles have however been shown to have lower paramagnetic susceptibility than large particles.  

Heats of adsorption of hydrogen on, and of dissolution in, supported palladium particles were size-independent down to 3 nm, but thereafter decreased significantly those of oxygen on rhodium, palladium and platinum fell with increasing size.  

The perovskite oxides are ionic compounds with an eledrostatic Madelung energy that is large enough to raise most cation outer s and p eledronic energies well above the top of the anion p bands, where they remain essentially unoccupied at ordinary temperatures. The exceptions are some A-site cations with 5s or 6s cores, such as Sn +, T1 +, Pb +, or Bi +. However, the empty 5s or 6s bands of cations Sn +, Tl +, Pb + or Bi +, located on the B-sites, are at low enough energies to accept eledrons. 

The five d orbitals of a transition metal atom B are degenerate however, with more than one electron in the d manifold, the spin degeneracy is removed by the ferromagnetic direct-exchange interaction between electron spins in atomic orthogonal orbitals. Transition metal B cations usually introduce filled and/or empty d states within the gap between the anion p bands and lanthanide 5d bands, which lowers the probability that the lanthanide ion can have two valence states in a transition metal perovsldte. 

Several perovskites exhibit metallic conductivity, typical examples being LaTi03, LaNi03, SrV03, AM0O3 (A = Ca, Sr, Ba), Re03, and A O. Metallic conductivity in similar perovskite oxides is due to a strong cation-anion-cation interaction [21,24,34]. 

The reason for these semiconductive properties of BaBi03 is the creation of two distinguishable Bi sites that change the translational symmetry of the crystal and split the 6s band into two. The substitution of Pb for Bi in BaBii Pbj 03 suppresses the disproportionation reaction, and introduces a metallic behavior for x 0.65 the system also becomes superconductive in the range 0.65 x 0.95 [69], as illustrated 

This is only a fleeting glance at a variety of electronic behavior of perovsldtes, and a comprehensive discussion of the electrical and magnetic properties of many perovskite compounds may be found in a series of reviews [34, 90-95]. 

Each carbon atom in the graphite structure contributes 4 valence electrons, resulting in 16 energy bands, 4 of them Jt-bands (two bonding and two antibonding) on either side of the Fermi level. In AB-stacked graphite, the separation between the 

ET Idnetics [34,101 -106] and whether the low DOS of graphite has a particularly significant effect [5]. 

While basal plane HOPG presents capacitance values of 2 pF cm in aqueous electrolytes [38,60,112,113], other graphite-like materials have much higher 

FIGURE 1.15 The band structure of free-standing suspended graphene. (From Rao, C. N. R. et al., J. Mater. Chem., 19, 2457, 2009. With permission of The Royal Society of Chemistry.) 

More importantly, massless charge carriers in graphene can give rise to a room temperature quantum Hall effect (QHE) that was exclusively observed in two-dimensional electron gas (2DEG) systems earlier. The QHE on graphene is different from conventional cases of semiconductor heterostructures because of the unique band structure. Generally, the Hall resistance as a function of concentration of electrons produces a series of plateaus at jh/2eB, which is referred to as integer 

FIGURE 1.16 (a) Ambipolar electric field effect in single-layer graphene. (With permission from Macmillan 

Publishers Ltd., Nat. Mater., 6, Geim, A. K. and Novoselov, K. S., 183, Copyright 2007.) (b) The half-integer quantum Hall effect in graphene. (With permission from Macmillan Publishers Ltd., Nature, 438, Novoselov, K. S. et al., 197, Copyright 2005.) 

Alloy Phase conversion AHkJ/ mol H2 ASJK-i mol H2 References 

Electron density calculations of the parent unsubstituted 1,2,4-tri-azolo[l,5-c]pyrimidine suggested that N4 and N6 caused a decrease of the 

The rather small dipole moment of the neutral depends strongly on the basis set and correlation treatment. Fortunately our interest lies in the (hyper)polarizabiUties. Nonetheless, we can say that our dipole moment results are in qualitative agreement with the value computed by Campbell et al. [5], but much smaller than reported by Li and Tomanek [40]. The comparison of our calculated (hyper)polarizabilities with those of Campbell et al. will be made later. We note that the addition of diffuse functions to the 6-31G basis is always crucial. But whereas the further addition of polarization functions has a minor effect on a and 7, for / they partially (or totally) offset the effect of the diffuse functions. Comparison of HF and (U)MP2 shows that correlation has a very large effect on / , but not a The fact that (U)B3LYP yields values similar to (U)MP2 suggests that both account fairly well for correlation (even though the calculations are only at the 6-3IG level). Due to the unavailability of 7 at 

As compared to the hypothetical non-interacting species the interaction between the Li+ cation and either the or Ceo cage leads to a moderate reduction of the diagonal polarizabilities and, in the case of [LiCeo] also of the second hyperpolarizabilities. The reduction for a may be due to a contraction of the electron density caused by the attraction of the cation. Such an explanation will not suffice for 7 since the effect of the interaction on the diagonal components is quite different for Li C6o, and the second hyperpolarizability is not simply related to the size of the electron distribution. The first hyperpolarizabilities arise from asymmetry of the charge distribution and are, consequently, strongly enhanced in the endohedral species. 

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Knowing the energy distributions of electrons, (k), and the spatial distribution of electrons, p(r), is important in obtaining the structural and electronic properties of condensed matter systems. 

Semiconductors are poor conductors of electricity at low temperatures. Since the valence band is completely occupied, an applied electric field caimot change the total momentum of the valence electrons. This is a reflection of the Pauli principle. This would not be true for an electron that is excited into the conduction band. However, for a band gap of 1 eV or more, few electrons can be themially excited into the conduction band at ambient temperatures. Conversely, the electronic properties of semiconductors at ambient temperatures can be profoundly altered by the... 

Several factors detennine how efficient impurity atoms will be in altering the electronic properties of a semiconductor. For example, the size of the band gap, the shape of the energy bands near the gap and the ability of the valence electrons to screen the impurity atom are all important. The process of adding controlled impurity atoms to semiconductors is called doping. The ability to produce well defined doping levels in semiconductors is one reason for the revolutionary developments in the construction of solid-state electronic devices. 

It is possible to use the quantum states to predict the electronic properties of the melt. A typical procedure is to implement molecular dynamics simulations for the liquid, which pemiit the wavefiinctions to be detemiined at each time step of the simulation. As an example, one can use the eigenpairs for a given atomic configuration to calculate the optical conductivity. The real part of tire conductivity can be expressed as... 

Hummel R 1985 Electronic Properties of Materials (New York Springer)... 

Madey T E, Guan J, Nien C-H, Dong C-Z, Tao H-S and Campbell R A 1996 Faceting induced by ultrathin metal films on W(111) and Mo(111) structure, reactivity, and electronic properties Surf. Rev. Lett. 3 1315... 

Wruck D A and Rubin M 1993 Structure and electronic properties of electrochromic NiO films J. Eiectrochem. See. 140 1097-104... 

Photoelectrochemistry may be used as an in situ teclmique for the characterization of surface films fonned on metal electrodes during corrosion. Analysis of the spectra allows the identification of semiconductor surface phases and the characterization of their thickness and electronic properties. 

The accuracy of most TB schemes is rather low, although some implementations may reach the accuracy of more advanced self-consistent LCAO methods (for examples of the latter see [18,19 and 20]). However, the advantages of TB are that it is fast, provides at least approximate electronic properties and can be used for quite large systems (e.g., thousands of atoms), unlike some of the more accurate condensed matter methods. TB results can also be used as input to detennine other properties (e.g., photoemission spectra) for which high accuracy is not essential. 

Flead and Silva used occupation numbers obtained from a periodic FIF density matrix for the substrate to define localized orbitals in the chemisorption region, which then defines a cluster subspace on which to carry out FIF calculations [181]. Contributions from the surroundings also only come from the bare slab, as in the Green s matrix approach. Increases in computational power and improvements in minimization teclmiques have made it easier to obtain the electronic properties of adsorbates by supercell slab teclmiques, leading to the Green s fiinction methods becommg less popular [182]. 

Vogel D, Kruger P and Pollmann J 1997 Structural and electronic properties of group-ill nitrides Phys. Rev. B 55 12 836, and references therein... 

Wachutka G, Fleszar A, Maca F and Scheffler M 1992 Self-consistent Green-function method for the calculation of electronic properties of localized defects at surfaces and in the bulk J. Phys. Condens Matter A 2831 Bormet J, Neugebauer J and Scheffler M 1994 Chemical trends and bonding mechanisms for isolated adsorbates on Al(111) Phys. Rev. B 49 17 242... 

Massobrio C, Pasquarello A and Corso A D 1998 Structural and electronic properties of small Cu clusters using generalized-gradient approximations within density functional theory J. Chem. Phys. 109 6626... 

Gronbeck H and Rosen A 1997 Geometric and electronic properties of small vanadium clusters a density functional study J. Chem. Phys. 107 10 620... 

As outlined above, electron transfer through the passive film can also be cmcial for passivation and thus for the corrosion behaviour of a metal. Therefore, interest has grown in studies of the electronic properties of passive films. Many passive films are of a semiconductive nature [92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102 and 1031 and therefore can be investigated with teclmiques borrowed from semiconductor electrochemistry—most typically photoelectrochemistry and capacitance measurements of the Mott-Schottky type [104]. Generally it is found that many passive films cannot be described as ideal but rather as amorjDhous or highly defective semiconductors which often exlribit doping levels close to degeneracy [105]. 

The molecular electronic polarizability is one of the most important descriptors used in QSPR models. Paradoxically, although it is an electronic property, it is often easier to calculate the polarizability by an additive method (see Section 7.1) than quantum mechanically. Ah-initio and DFT methods need very large basis sets before they give accurate polarizabilities. Accurate molecular polarizabilities are available from semi-empirical MO calculations very easily using a modified version of a simple variational technique proposed by Rivail and co-workers [41]. The molecular electronic polarizability correlates quite strongly with the molecular volume, although there are many cases where both descriptors are useful in QSPR models. 

Ohlaiii a new stable structure as a starting point for a single point, quantum mechanical calculation, which provides a large set ol structural and electronic properties. 

Each of these tools has advantages and limitations. Ab initio methods involve intensive computation and therefore tend to be limited, for practical reasons of computer time, to smaller atoms, molecules, radicals, and ions. Their CPU time needs usually vary with basis set size (M) as at least M correlated methods require time proportional to at least M because they involve transformation of the atomic-orbital-based two-electron integrals to the molecular orbital basis. As computers continue to advance in power and memory size, and as theoretical methods and algorithms continue to improve, ab initio techniques will be applied to larger and more complex species. When dealing with systems in which qualitatively new electronic environments and/or new bonding types arise, or excited electronic states that are unusual, ab initio methods are essential. Semi-empirical or empirical methods would be of little use on systems whose electronic properties have not been included in the data base used to construct the parameters of such models. 

Finally, the solvent also interacts with sites of the Lewis acid and the Lewis base that are not directly involved in mutual coordination, thereby altering the electronic properties of the complex. For example, delocalisation of charges into the surrounding solvent molecules causes ions in solution to be softer than in the gas phase . Again, water is particularly effective since it can act as an efficient electron pair acceptor as well as a donor. 

Whatever the method employed and its degree of sophistication some common trends can be noted in the electronic properties of the thiazole molecule. 

Turning now to electrophilic aromatic substitution in (trifluoromethyl)benzene we con sider the electronic properties of a trifluoromethyl group Because of their high elec tronegativity the three fluorine atoms polarize the electron distribution m their ct bonds to carbon so that carbon bears a partial positive charge... 

Any set of one-electron functions can be a basis set in the LCAO approximation. However, a well-defined basis set will predict electronic properties using fewer terms than a poorly-defined basis set. So, choosing a proper basis set in ab initio calculations is critical to the reliability and accuracy of the calculated results. 

HyperChem always computes the electronic properties for the molecule as the last step of a geometry optimization or molecular dynamics calculation. However, if you would like to perform a configuration interaction calculation at the optimized geometry, an additional single point calculation is required with the Cl option being turned on. 

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