Photo-induced absolute negative current in a molecular electronic system.Alex Prociuk and Barry D. Dunietz,
Submitted,
manuscript available for download (2009)
Negative current in a symmetric 3-state molecular model system can
emerge in response to population inversion of electronic excited states induced
by photo excitations. The negative current results from the stronger
resonance of the populated higher excited band with the source
electrode than with the drain, while the lower excited state remains
unoccupied. In our treatment, the electronic equations of motion are
represented using non-equilibrium Green's functions implementing the
Keldysh formalism. Their solution is achieved by using time-dependent
perturbation theory.
Gating dependence of single molecule field effect transistors on contact symmetry
Trilisa Perrine and Barry D. Dunietz,
Submitted,
manuscript available for download (2009)
The geometric aspects for the functionality of a molecular-based field
effect transistor (FET) are analyzed. A computational study is
performed on molecular models involving a well defined conjugation
plane coupled to gold-based electrodes through thiol
bonding. Transport gating of the FET is shown to depend on a
symmetry-breaking effect induced by the gating-field. This effect is
also related to the orientation of the field relative to the
gold-thiol bonds, the molecular conjugation plane, and the overall
symmetry of the device. It is found that the presence of a center of
inversion in the bulk-coupled molecular system results in the
cancellation of the transisting response. The presence of a plane of
symmetry which includes the transport vector, in a reduced symmetry
system, results in a gating response only to electric fields oriented
perpendicular to that mirror plane.
Modeling transient aspects of coherence-driven electron transport
Alex Prociuk, Heidi Phillips and Barry D. Dunietz,
Submitted,
manuscript available for download (2009)
Non-equilibrium Green's function formalism (NEGF) by employing
time-dependent perturbation theory is used to solve the electronic
equations of motion of model systems under potential biasing
conditions. The time propagation is performed in the full frequency
domain of the two time variables representation. We analyze
transient aspects of the conductance under applied direct-current
and alternating current potential perturbation. The coherence
induced response dependence on different aspects of the applied
perturbation are resolved in time and analyzed using TD distribution
of the current operator.
Bias-induced electronic spectral effects of molecular junctions: A computational analysis
Heidi Phillips, Alex Prociuk and Barry D. Dunietz,
Submitted,
__ (2009)
___
On the Electronic Spectra of a Molecular Bridge Under
Non-Equilibrium Electric Potential Conditions
Alex Prociuk and Barry D. Dunietz,
Accepted,
Chapter in Atomic and Molecular Systems, Dynamics, Spectroscopy,
Clusters, and Nanostructures, Springer publisher, Available for download (2009)
The linear response of the electronic density of a molecular-based
junction under potential bias conditions to a probing polarizing
perturbation is calculated to model the electronic spectra. It is
shown that steady flux conditions lead to dramatic effects on the
electronic spectra of the confined system. The non-equilibrium
conditions enable electronic transitions that are otherwise forbidden.
The implemented methodology uses the Keldysh contour formalism to
express the electronic equations of motion. The related time
correlation Green Functions are then solved for in the full frequency
representation and at the linear response level.
Enhanced Conductance via Induced &Pi-Stacking Interactions in Cobalt(II) Terpyridine Bridged Complexes
Trilisa Perrine, and Barry D. Dunietz,
J. Phys. Chem. B.,
112 (2008) 16070 -16075 .
Computational
model systems are used to explore improving the transmission through a
molecular device based on bridged cobalt(II) complexes. The bridging
ligands and the organic conjugated molecular ligands are altered to
improve the current flow through both an enhanced &Pi-stacking
interaction as well as involving the metal ions directly in the
conduction pathway. With terpyridine as the organic ligand, both
acetate and NH2- produce conductive devices, while a terpyridine
complex bridged by Cl- is not conductive. The addition of a fused
ring on either end of the conjugated molecule has a complex effect
which is sensitive to the bridged ligand and the particular geometry
of the complex.
Time-dependent current through electronic channel models using a mixed time-frequency
solution of the equations of motion
Alexander Prociuk and Barry D. Dunietz
Phys. Rev. B,
78
(2008) 165112.
A non-equilibrium Green's-Function (NEGF) model based on time
dependent perturbation theory is developed to propagate electronic
structure and molecular conductance of extended
electrode-molecule-electrode nanostructures. In this model, we use
the two time variable nature of the Kadanoff-Baym equations of motion
to formulate a mixed time-frequency representation for the electronic
density expressed by the appropriate GF (G$^<$). This allows for the
dynamical treatment of open systems. Furthermore, highly informative
time dependent Wigner distributions are used to shed light on the
features of dynamical observables, such as electron current.
Calculations, performed on model systems, resolve the dynamic current
into direct and alternating components. The direct current is due to
electronic open channels near the Fermi level and the alternating
response is due to interference fringes from a superposition of
extended states. We analyze the transient conductance with respect to
the fundamental system's parameters, the effect of bound states and
conductance driven by laser induced coherence affected by detuning due
to an applied DC bias. The amplitude of the alternating transient
current can be adjusted by reshaping the bias pulse or by controlling
the electronic coupling terms. Bound states may yield a persisting
oscillating response depending on their relative electronic densities.
In the analysis we utilize the calculated highly informative
time-dependent current distributions.
Ab initio study of charge transport of hydrogen functionalized palladium wiresZhen Zhao, and Barry D. Dunietz,
J. Chem. Phys,
129 (2008) 024702.
We present ab initio calculations of transport properties of palladium
wires in the presence of hydrogen. Detailed investigations have been
1conducted with a pure palladium wire and with opening a gap inside the
wire in which the transition between point contact regime and
tunneling regime occurs. The effect of the presence of hydrogen in the
gap is studied for different ranges of the gap size. The hydrogen
mediated transport in the contact and tunneling regimes of the gap are
analyzed and compared. It is predicted that only in large enough
distances the hydrogen presence increases the conductance. The effect
of additional hydrogen molecules on the gap is also studied.
Synthetic, mechanistic, and computational investigations of nitrile-alkyne cross-metathesis
Andrea M. Geyer, Eric S. Wiedner, J. Brannon Gary, Robyn L. Gdula, Nicola C. Kuhlmann, Marc J. A. Johnson, Barry D. Dunietz, Jeff W. Kampf
J. Amer. Chem. Soc. ,
130 (2008) 8994-8999.
The terminal nitride complexes NW(OC(CF3)2Me)3(DME) (1-DME), [Li(DME)2][NW(OC(CF3)2Me)4] (2), and [NW(OCMe2CF3)3]3 (3) were prepared in good yield by salt elimination from [NWCl3]4. X-ray structures revealed that 1-DME and 2 are monomeric in the solid state. All three complexes catalyze the cross-metathesis of 3-hexyne with assorted nitriles to form propionitrile and the corresponding alkyne. Propylidyne and substituted benzylidyne complexes RCW(OC(CF3)2Me)3 were isolated in good yield upon reaction of 1-DME with 3-hexyne or 1-aryl-1-butyne. The corresponding reactions failed for 3. Instead, EtCW(OC(CF3)Me2)3 (6) was prepared via the reaction of W2(OC(CF3)Me2)6 with 3-hexyne at 95 N0C. Benzylidyne complexes of the form ArCW(OC(CF3)Me2)3 (Ar = aryl) then were prepared by treatment of 6 with the appropriate symmetrical alkyne ArCCAr. Three coupled cycles for the interconversion of 1-DME with the corresponding propylidyne and benzylidyne complexes via [2 + 2] cycloaddition$(B!](Bcycloreversion were examined for reversibility. Stoichiometric reactions revealed that both nitrile-alkyne cross-metathesis (NACM) cycles as well as the alkyne cross-metathesis (ACM) cycle operated reversibly in this system. With catalyst 3, depending on the aryl group used, at least one step in one of the NACM cycles was irreversible. In general, catalyst 1-DME afforded more rapid reaction than did 3 under comparable conditions. However, 3 displayed a slightly improved tolerance of polar functional groups than did 1-DME. For both 1-DME and 3, ACM is more rapid than NACM under typical conditions. Alkyne polymerization (AP) is a competing reaction with both 1-DME and 3. It can be suppressed but not entirely eliminated via manipulation of the catalyst concentration. As AP selectively removes 3-hexyne from the system, tandem NACM-ACM-AP can be used to prepare symmetrically substituted alkynes with good selectivity, including an arylene-ethynylene macrocycle. Alternatively, unsymmetrical alkynes of the form EtCCR (R variable) can be prepared with good selectivity via the reaction of RCN with excess 3-hexyne under conditions that suppress AP. DFT calculations support a [2 + 2] cycloaddition$(B!](Bcycloreversion mechanism analogous to that of alkyne metathesis. The barrier to azametalacyclobutadiene ring formation/breakup is greater than that for the corresponding metalacyclobutadiene. Two distinct high-energy azametalacyclobutadiene intermediates were found. These adopted a distorted square pyramidal geometry with significant bond localization.
Accessing Metal-Carbide Chemistry. A Computational Analysis of Thermodynamic Considerations
J. Brannon Gary, Corneliu Buda, Marc J. A. Johnson, and Barry D. Dunietz,
Organometallics,
27 (2008) 814.
The electronic structures of terminal metal carbide complexes are
calculated using DFT. This study outlines the factors that give rise
to stable carbide complexes, which can be used to help in the
synthesis of new carbide complexes and to tune their stability as
desired. The calculations reveal the presence of a strong Ru$\equiv$C triple
(\sigma + 2\pi) bond. The C atom is nearly unhybridized, such that the
C-component of the Ru-C \sigma-bond has 90% 2p character. This leaves a
very stable carbon-based lone pair that is almost entirely 2s in
character, which accounts for the lack of Lewis base character
exhibited experimentally. Calculations predict a Ru-C bond
dissociation energy of 147.4 kcal mol^{-1} in a typical Ru carbide
complex. This large bond strength is not unique to the RuC bond, as
revealed by an extension of the study to identify schemes by which to
chemically tune the metal-carbide bond strength. Methods examined to
achieve this tuning include changing the identity of the central metal
and altering the metal ligation scheme. In general, 16-electron
square-pyramidal M(C)L_4 complexes and 12- or 16-electron tetrahedral
M(C)L_3 complexes of the 4d elements can possess comparably strong
metal-carbide bonds. The calculations also show that the carbide
moiety exerts a very strong trans influence, which explains several
experimental observations. We conclude that the dearth of terminal
carbide complexes is not due to any inherent weakness of M\equiv C
bonds. Many more terminal carbide complexes can be expected in the
future as new routes to their formation are found.
Gating of single molecule transistors: Combining field-effect and chemical control
Trilisa M. Perrine, Ron G. Smith, Christopher Marsh, and Barry D. Dunietz,
Journal of Chemical Physics,
128 (2008) 154706.
Previously we have demonstrated that several structural features
are crucial for the functionality of molecular field effect transistors.
The effect of additional
structural aspects of molecular wires is explored.
These include the type of, the thiol binding location on, and the chemical substitutions of a conjugated
system. Pentacene, porphyrin and the Tour-Reed devices are utilized as model
systems.
The thiol binding location is shown to have a varried effect on the transmission
of a system depending on the molecular orbitals involved.
Substitution by electron withdrawing and donating groups is illustrated
to have a substantial effect on the transmission of single molecule devices.
The substituation effect is either a simple energy shifting effect
or a more complicated
resonance effect, and can be used to effectively tune the electronic behavior of a single molecule field effect transistor.
Conductance of a cobalt(II) terpyridine complex based molecular transistor: A computational analysis
Trilisa M. Perrine and Barry D. Dunietz,
Journal of Physical Chemistry A: Lester Special Issue,
112 (2008), 2043-2048.
A recent experiment, in which a molecular transistor based on the coordination chemistry of cobalt(II) and organic self-assembly-monolayers is formed by means of self-aligned lithography, is analyzed with a computational approach. The calculations reveal that a complex involving two cobalt(II) ions bridged by acetate ions can effectively span the nano-gap. This bridged complex is shown to be both more flexible and more conductive than the alternative structure involving a
single cobalt(II) ion. The single cobalt(II) ion complex is the more stable structure in a non-confined environment (i.e. in solution), but is found to be less effective at connecting the leads of the fabricated gap and is less
likely to result in a conductive device.
Carbonyl mediated conductance through metal bound peptides; a computational study
Trilisa M. Perrine and Barry D. Dunietz,
Nanotechnology,
18, (2007), 424003.
Large increases in the conductance of peptides, upon binding to metal ions, have been recently reported experimentally. The mechanism of the conductance switching is examined computationally. It is suggested that oxidation of the metal ion occurs after binding peptide. This is caused by the bias potential placed across the metal-peptide complex. A combination of configurational changes, metal ion involvment and interactions between carbonyl group oxygen atoms and the gold leads are all shown to be necessary for the large improvement in the conductance seen experimentally. Differences in the molecular orbitals of the nickel and copper complexes are noted and serve to explain the variation of the conductance improvement upon binding to either a nickel or copper ion.
Theoretical Studies of Conjugation Effects on Excited State Intramolecular Hydrogen-atom
Transfer Reactions in Model Systems
Carlos Biaz and Barry D. Dunietz,
Journal of Physical Chemistry A,
111, (2007), 10139-10143.
Intramolecular Hydrogen-atom transfer dependence on electronic
conjugation of curcumin and related molecular models in the ground
state and 1&pi &pi* excited state are computationally studied at
first-principles electronic structure level. The larger, more
conjugated, systems exhibit a lower reaction barrier in the ground
state but a higher barrier in the excited state. This is associated
with a smaller increase in the conjugation upon excitation in the
larger systems. Our studies provide a detailed description and
analysis of these energy trends as well as an insight into the
physical nature of the intramolecular hydrogen-atom transfer
reactions.
Fragmentation pathways and mechanisms of aromatic compounds in atmospheric pressure studied by GC-DMS and DMS-MS
Shai Kendler, Gordon R. Lambertus, Barry D. Dunietz, Stephen L. Coy, Erkinjon G. Nazarov, Raanan A. Miller, and Richard D. Sacks,
Int. J. of Mass Spec. ,
263, (2007), 137-147.
Differential mobility spectrometry (DMS) is a highly sensitive sensing technology capable of selecting and detecting ions based on the difference between ion mobility at high and low electric field. The combination of a micro-fabricated DMS with gas chromatography (GC) has allowed extensive investigation of the ion chemistry and collisionally induced dissociation (CID) of diaryl molecules on a millisecond timescale at temperatures up to 130 degrees C. DMS-pre-filtered time-of-flight mass spectrometry (DMS-MS) has been used to verify the chemical composition of the ion species resolved by GC-DMS. This work focuses on the fragmentation of diaryl compounds, including diphenyl methane (DPM) and bibenzy] (BB), using information from the DMS and DMS-MS spectra of a series of aromatic compounds. Density functional theory calculations have been used to investigate the geometry and the energy along the reaction coordinate for the loss of benzene from DPM-H+ and BB-H+ for comparison with GC-DMS and DMS-MS experimental results and with previously reported chemical ionization MS. DPM-H+ is observed to undergo field-induced fragmentation in the DMS to produce C7H7+(Bz(+)) and unobserved neutral benzene with a low energy barrier. In contrast, BB-H+ fragments to C8H9+ and benzene with a higher energy barrier. Calculated barriers and experimental results are in qualitative agreement. Depletion of the ionized fragments in favor of ion-neutral clusters was also observed at higher concentrations. It is suggested that CID in DMS can further enhance DMS analytical performance.
Single-molecule field-effect transistors: A computational study of the effects of contact geometry and gating-field orientation on conductance-switching properties
Trilisa M. Perrine and Barry D. Dunietz,
Phys. Rev. B,
75, (2007), 195319.
The relation of geometric features to the effect of gating electric fields on the conductance through conjugated systems is investigated by electronic transmission calculations employing Green's function based modeling. Switching is only induced if the field is applied in an orientation which results in energy shifting of the molecular orbitals. This is found to depend on the orientation of the field with respect to the plane defined by the molecular conjugation. The switching can be quenched by structural rearrangement of the chemical bonds to the bulk, where the relative position of the electrodes is modified.
Electron Transport through Heterogeneous Intermolecular Tunnel Junctions
Das, M. and Dunietz, B. D.,
J. Phys. Chem. C.,
111, (2007), 1535--1540.
Quantum charge transport through intermolecular tunnel junctions is studied. Intermolecular tunnel junctions can be defined by the end groups of pairs of self-assembled monolayers of functionalized conjugated alkenes on gold surfaces. Conductivity dependence on the tunnel distance has been compared for various junctions. It is found that for junctions dominated by attractive interactions, for example, systems involving hydrogen bonding, conductivity exhibits less dependence on the tunneling distance than with junctions dominated by dispersive interactions. Junctions with stronger distance dependence conductivty are desired for applications related to chemical sensors. Our study provides insight for designing an efficient chemical sensor that is based on heterogeneous tunnel junction, which may involve conductivity through a combination of the attractive hydrogen-bonding channel and repulsive dispersive interactions.
Benchmarking the performance of density functional theory based Green's function formalism utilizing different self-energy models in calculating electronic transmission through molecular systems
Prociuk, A. and Dunietz, B.D.,
J. Chem. Phys.,
125, (2006), 204717.
Electronic transmission through a metal-molecule-metal system is calculated by employing a Green's function formalism in the scattering based scheme. Self-energy models representing the bulk and the potential bias are used to describe electron transport through the molecular system. Different self-energies can be defined by varying the partition between device and bulk regions of the metal-molecule-metal model system. In addition, the self-energies are calculated with different representations of the bulk through its Green's function. In this work, the dependence of the calculated transmission on varying the self-energy subspaces is benchmarked. The calculated transmission is monitored with respect to the different choices defining the self-energy model. In this report, we focus on one-dimensional model systems with electronic structures calculated at the density functional level of theory.
Spin-dependent electronic transport through a porphyrin ring ligating an Fe(II) atom: An ab initio study
Chen, Y. and Prociuk, A. and Perrine, T. and Dunietz, B.D.,
Phys. Rev. B,
74, (2006), 245320.
Conductance calculations employing density functional theory methodology and Landauer formalism predict that a ligated iron atom can be used as a switching device. The iron atom is ligated in our models by a porphyrin molecule. The iron-porphyrin molecular device is shown to lose more than 66% of its conductance by shifting from the low spin coupling state to excited spin states. Further reduction is also correlated with a mechanical distortion of the porphyrin plane. Both the distortions and spin transitions are fast processes that can be invoked by manipulating the iron's ligation scheme through the axial ligands.
Hydrogen Physisorption on the Organic Linker in Metal Organic Frameworks: Ab Initio Computational Study
Buda, C. and Dunietz, B.D.,
J. Phys. Chem. B.,
110, (2006), 10479--10484.
Research for materials offering efficient hydrogen storage and transport has recently received increased attention. Metal organic frameworks (MOFs) provide one promising group of materials where several recent advances were reported in this direction. In this computational study ab initio methods are employed to study the physisorption of hydrogen on conjugated systems. These systems are used as models for the organic linker within MOFs. Here, we focus on the adsorption sites related to the organic linker with special attention to the edge site, which was only recently reported to exist as the weakest adsorbing site in MOFs. We also investigate chemically modified models of the organic connector that result in enforcing this adsorption site. This may be crucial for improving the uptake properties of these materials to the goal defined by DOE for efficient hydrogen transport materials.
Metathesis-Enabled Formation of a Terminal Ruthenium Carbide Complex: A Computational Study
Buda, C., Caskey, S.R., Johnson, M.J.A. and Dunietz, B.D.,
Org. Metal.,
25, (2006), 4756-4762.
The energy profile of rare Ru carbide formation starting from an acetoxycarbene complex is studied using DFT methods. Three distinctive reaction pathways that differ in their initiation step are investigated. Two of the proposed reaction mechanisms have relatively similar activation barriers. Therefore, additional calculations have been performed using large size ligands (PCy3), matching exactly the actual experimental system. In addition, the corresponding kinetic isotope effect has been evaluated and compared to the experimental measured value.
Advances in methods and algorithms in a modern quantum chemistry program package.
Shao, Yihan, Molnar, Laszlo Fusti, Jung, Yousung, Kussmann, Jorg, Ochsenfeld, Christian, Brown, Shawn T., Gilbert, Andrew T.B., Slipchenko, Lyudmila V., Levchenko, Sergey V., O'Neill, Darragh P., Jr, Robert A. DiStasio, Lochan, Rohini C., Wang, Tao, Beran, Gregory J.O., Besley, Nicholas A., Herbert, John M., Lin, Ching Yeh, Voorhis, Troy Van, Chien, Siu Hung, Sodt, Alex, Steele, Ryan P., Rassolov, Vitaly A., Maslen, Paul E., Korambath, Prakashan P., Adamson, Ross D., Austin, Brian, Baker, Jon, Byrd, Edward F. C., Dachsel, Holger, Doerksen, Robert J., Dreuw, Andreas, Dunietz, Barry D., Dutoi, Anthony D., Furlani, Thomas R., Gwaltney, Steven R., Heyden, Andreas, Hirata, So, Hsu, Chao-Ping, Kedziora, Gary, Khalliulin, Rustam Z., Klunzinger, Phil, Lee, Aaron M., Lee, Michael S., Liang, WanZhen, Lotan, Itay, Nair, Nikhil, Peters, Baron, Proynov, Emil I., Pieniazek, Piotr A., Rhee, Young Min, Ritchie, Jim, Rosta, Edina, Sherrill, C. David, Simmonett, Andrew C., Subotnik, Joseph E., III, H. Lee Woodcock, Zhang, Weimin, Bell, Alexis T. and Chakraborty, Arup K.,
Phys. Chem. Chem. Phys.,
8, (2006), 3172-3191.
Additional Manuscripts and Papers:
"Gating field effect dependence on contact geometry symmetry of
single molecule conjugated transistors" Trilisa Perrine, and Barry D. Dunietz (To be submitted to PRB).
" Beyond 7-Azaindole: Theoretical studies of conjugation effects on intermolecular double hydrogen-atom transfer reaction"
Carlos Baiz, Sarah Ledford, Kevin Kubarych and Barry D. Dunietz (Submitted to JPCA).
"Hydrogen interaction with organic conjugated molecule: Multi adsorption, multi site adsorption and ring modification effects on hydrogen uptake of candidates for organic linker in metal organic frameworks" Miguel Wong, Ben Van-Kuiken, Corneliu Buda and Barry D Dunietz.
Articles Before 2005:
Ugalde, J. M., Dunietz, B., Dreuw, A., Head-Gordon, M. and Boyd, R. J. `The spin
dependence of spatial size of Fe(II) and of the structure of Fe(II)-porphyrins.' J. Phys. Chem. A., 108, (2004), 4653-4657.
Dunietz, B. D., Markovic, N., Ross, P. H. and Head-Gordon, M. `Initiation of Electrooxidation of CO on Pt based electrodes at full coverage conditions simulated by ab-initio electronic structure calculations.' J. Phys. Chem. B., 108, (2004), 9888.
Saravanan*, C., Dunietz*, B. D., Markovic, N., Somorjai, G. and Head-Gordon,
M. Ross, P. H. `Electro-oxidation of CO on Pt electrodes simulated by electronic structure calculations.' J.Electroanal.Chem., J. Weaver Special memorial issue (v554), (2003), 459.
Dunietz, B. D. and Head-Gordon, M. `Manifestations of symmetry breaking in selfconsistent eld electronic structure calculations.' J. Phys. Chem. A., 107, (2003), 9160.
Head-Gordon, M., Van Voorhis, T., Beran, G. J. O. and Dunietz, B. D. `Local correlation models.' Computational Science - ICCS 2003, Pt IV , 2660, (2003), 96-102.
Dunietz, B. D., Dreuw, A. and Head-Gordon, M. `Initial steps of the photodissociation of the CO ligated heme group.' J. Phys. Chem. B., 107, (2003), 5623-5629.
Dunietz, B. D., van Voorhis, T. and Head-Gordon, M. `Geometric direct minimization of Hartree Fock calculations involving open shell wavefunctions with spin restricted orbitals.' J. Theo. and Comp. Chem., 1, (2002), 255-261.
Dreuw, A., Dunietz, B. D. and Head-Gordon, M. `Characterization of the relevant
excited states in the photodissociation of the CO-ligated Hemoglobin and Myoglobin.'
J. Am. Chem. Soc., 124, (2002), 12070-12071.
Dunietz, B. D. and Friesner, R. A. `Application and development of multicongurational localized perturbation theory.' J. Chem. Phys., 115, (2001), 11052.
Friesner, R. A. and Dunietz, B. D. `Large-scale ab-initio quantum chemical calculations on biological systems.' Accounts Chem Res, 34, (2001), 351-358.
Gherman, B. F., Dunietz, B. D., Whittington, D. A., Lippard, S. J. and Friesner, R. A. `Activation of the C-H bond of methane by intermediate Q of methane monooxygenase:
A theoretical study.' J. Am. Chem. Soc., 123, (2001), 3836.
Dunietz, B. D., Beachy, M. D., Cao, Y. X., Whittington, D. A., Lippard, S. J. and
Friesner, R. A. `Large scale ab-initio quantum chemical calculation of the intermediate
in the soluble methane monooxygenase catalytic cycle.' J. Am. Chem. Soc., 122, (2000), 2828.
Friesner, R. A., Murphy, R. B., Beachy, M. D., N., Ringnalda M., Pollard, W. T.,
Dunietz, B. D. and Cao, Y. X. `Correlated ab-initio electronic structure calculations
for large molecules.' J. Phys. Chem. A., 103, (1999), 1913.
Dunietz, B. D., Murphy, R. B. and Friesner, R. A. `Calculation of atomization energies by a multicon gurational localized perturbation theory - Application for closed shell cases.' J. Chem. Phys., 110, (1999), 1921.
