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Topic: Potential energy surface

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	Potential energy - Wikipedia, the free encyclopedia
		Potential energy is energy that is "captured" in an object, with the potential to be released.
		Gravitational potential energy is the energy that would be released if an object in a gravitational field (such as the earth's gravitational field) were allowed to fall from its current position to a given reference level (such as the surface of the earth).
		The factors that affect an object's gravitational potential energy are: the mass of the object, the distance that it is raised, and the gravitational field strength.
	en.wikipedia.org /wiki/Potential_energy (2228 words)

	energy - Hutchinson encyclopedia article about energy (Site not responding. Last check: 2007-10-30)
		Energy can be converted from one form to another, but the total quantity in a system stays the same (in accordance with the conservation of energy principle).
		Energy is transferred from one form to another, but the sum total of the energy after the conversion is always the same as the initial energy.
		Energy may be likened to the bending of a crossbow; decision, to the releasing of a trigger.
	encyclopedia.farlex.com /energy (1205 words)

	Potential energy surface - Wikipedia, the free encyclopedia
		A potential energy surface is generally used within the adiabatic or Born-Oppenheimer approximation in quantum mechanics and statistical mechanics to model chemical reactions and interactions in simple chemical and physical systems.
		There is a natural correspondence between potential energy surfaces as they exist (as polynomial surfaces) and their application in potential theory, which associates and studies harmonic functions in relation to these surfaces.
		For example, the Morse potential and the simple harmonic potential well are common one-dimensional potential energy surfaces (potential energy curves) in applications of quantum chemistry and physics.
	en.wikipedia.org /wiki/Potential_energy_surface (130 words)

	Potential_energy
		Potential energy is energy which depends on mutual positions of bodies.
		The energy is defined as a work against a specific force such as gravity, an elastic force of a spring in a clockwork motor, electric force, etc (and is usually named after that specific force).
		The factors that affect the amount of gravitational potential energy that is created are: the mass of the object, the distance that it is raised and the gravitational field strength.
	www.brainyencyclopedia.com /encyclopedia/p/po/potential_energy.html (1732 words)

	Diatomic Molecules - Potential Energy Surfaces
		We saw in section 3.1 that the potential energy surface of a molecular system is defined as the electronic potential energy including nuclear repulsion, at a given nuclear configuration (equation (3.8)).
		A potential energy surface is the result of solving equation (3.6) for many nuclear configurations – giving the electronic potential energy including nuclear repulsion of the system as a function of the nuclear coordinates.
		It describes the potential energy of the system, U(R), as the two atoms are brought closer to, or moved away from, one another (Figure 4.1).
	www.chm.bris.ac.uk /webprojects2002/grant/webcomp/diatomicpes.html (317 words)

	Energy (Site not responding. Last check: 2007-10-30)
		While kinetic energy is the portion of a system's energy associated with motion, potential energy is the energy of a system associated with the spatial configuration of the system's components and their interaction(s) with each other.
		This relationship demonstrates that the force between the objects is in the direction of decreasing potential energy, and the magnitude of the force is proportional to the extent to which potential energy decreases.
		Internal energy is the kinetic energy associated with the motion of molecules, and the potential energy associated with the rotational, vibrational and electric energy of atoms within molecules.
	www.freedownloadsoft.com /info/energy.html (2168 words)

	Cerius2 Forcefield Based Simulations - Forcefields
		3 is the Schrödinger equation for the motion of the nuclei on the potential energy surface.
		This energy expression is the equation that describes the potential energy surface of a particular model as a function of its atomic coordinates.
		Quantum calculations of the energy surfaces of a series of model compounds (equilibrium structures, models at conformational energy barriers, and distorted structures) yield energies as well as their derivatives with respect to atomic coordinates (i.e., the surface gradients and curvatures) (Maple et al.
	www.chem.cmu.edu /courses/09-560/docs/msi/ffbsim/2_Forcefields.html (8444 words)

	Potential-energy-surface calculations.
		The configuration energy in the LN approach is given by,
		In order to obtain the configuration dependent PES for a given multi-qp state, a process of diabatic blocking is necessary, where the given orbitals which are occupied by the specified quasiparticles are followed and blocked.
		The nuclear shape is thus obtained by minimizing the calculated potential energy in the quadrupole (
	www.pa.uky.edu /~jnorce/Nuclear/node7.html (584 words)

	Re-engineering potential energy surfaces
		In contrast, the energy values for the transition states corresponding to the cycloelimination of the trans- isomer 12 are higher in energy than these obtained for the ring opening transformations 8 in all the examples except 8e (Table 2).
		Overall, the low energy barriers computed for 6d and 6e in particular suggest that the synchronous reaction pathway for these two systems in particular should be readily accessible under thermal conditions, and that experimental verification could be sought for this system.
		The sum of the squares of the coefficients at the carbon atom a to R is 0.348 and b is 0.015.
	www.rsc.org /suppdata/perkin2/1998/2695/index.html (1896 words)

	The Standard Potential Energy Surface
		In the microcanonical ensemble the kinetic energy increases as the potential energy decreases.
		The entropy bottleneck occurs because at lower potential energy the loss in entropy due to the reduced number of minima is not completely compensated by the greater vibrational entropy that results from the larger kinetic energy.
		This is reflected in the time evolution of the probability distribution: the probabilities of occupying higher potential energy levels rapidly attain approximate local equilibrium values which then slowly decay as the global minimum becomes more populated (Figure 5.5c).
	www-wales.ch.cam.ac.uk /~jon/PhD2/node36.html (1697 words)

	Computational Organic Photochemistry
		For a diatomic molecule its potential energy surface is a two dimensional plot with the inter nuclear separation (the only degree of freedom) on the x-axis and the energy at that bond distance on the y-axis, producing a curve (the so-called Morse curve, see Figure 1).
		In classical mechanics, the first derivative of the potential energy for a particle is minus the force on the particle, and the second derivative (for a quadratic potential) is the force constant.
		Observe the shape of the ground state surface in the region of the conical intersection in Figure 3.
	ccmaol1.chim.unisi.it /comp-photochem/lecture1.html (2902 words)

	Calculating potential energy surfaces
		To construct a potential energy surface, we need to be able to calculate the energy of the molecule at a particular geometry.
		The potential energy surface (curve) for a diatomic molecule is easy to visualize – it is a function simply of the interatomic distance.
		To optimize molecular geometries (to find minima and transition states), or to simulate the dynamics of a molecule, we need a technique capable of calculating the energy of a molecular structure, and the first (and preferably second) derivatives of the energy with respect to the coordinates of the molecule.
	www.chm.bris.ac.uk /pt/ajm/mmhtm/MM_L1p3.htm (295 words)

	CHEMISTRY: ON SURFACE POTENTIAL ENERGY LANDSCAPES
		For carbon monoxide copper (001), the authors measure the diffusion-induced energy broadening in the scattered helium beam and extract properties of the adsorbate-substrate potential.
		Atoms in the surface of the catalyst may form chemical bonds with atoms in impinging molecules, a phenomenon known as "chemisorption".
		Similar considerations apply to the surfaces of solid catalysts in general and of metal oxides in particular, because the surface atoms are characterized by a "ligand" sphere that differs from that in the bulk.
	scienceweek.com /2004/sc040820-3.htm (1058 words)

	Chem&Bio News - When Is a Minimum Not a Minimum? - ChemBioNews.Com 11.2
		For example, for a diatomic molecule, the potential energy surface can be represented by a two-dimensional plot with the internuclear separation on the X-axis and the energy at that bond distance on the Y-axis; in this case the potential energy surface is a curve.
		A point on the potential energy surface where the forces are zero is called a stationary point.
		When you perform a minimization, intending to find the minimum energy structure, there are several possibilities as to the nature of the results: you may have found the global minimum, you may have found a local minimum but not the global minimum, or you may have located a saddle point.
	chemnews.cambridgesoft.com /art.cfm?S=155 (1148 words)

	e-Prints Soton - The intermolecular potential energy surface of the He·NO+ cationic complex
		Close-coupling calculations of bound rotational and vibrational states are carried out on a new intermolecular potential energy function based on 200 energies of the He·NO+ cationic complex calculated at the coupled-cluster single double (triple)/aug-cc-pV5Z ab initio level of theory at a range of geometries and point-by-point corrected for basis set superposition error.
		The potential energy function is constructed by combining the reciprocal power reproducing kernel Hilbert space interpolation with Gauss–Legendre quadrature.
		The best estimate of the intermolecular dissociation energy, De, is 198±4 cm–1, obtained by extrapolations to the complete basis set limit, and calculating estimates for relativistic effects and core and core-valence correlation effects.
	eprints.soton.ac.uk /19857 (205 words)

	The concept of a Potential Energy Surface
		Since the potential depends on the nuclear coordinates, the electronic wavefunctions depends parametrically on R and the "eigenvalue" E
		The validity of this separation between electronic and nuclear motion is due to the large ratio between electronic and nuclear masses.
		The key element in Classical Molecular Dynamics is to replace a quantum mechanical description of the nuclear motion by a classical one, and where the potential energy function in the classical description is in principle the quantum mechanical potential energy surface (PES)
	www.phys.uit.no /~inge/ttp5/concept-of-pes.htm (313 words)

	Potential Energy Encyclopedia Article @ LaunchBase.net (Launch Base) (Site not responding. Last check: 2007-10-30)
		This page contains quite a lot of relevant information about Potential energy.
		The most widely used form of the gravitational potential function depends on (latitude) and potential coefficients, Jn, called the zonal coefficients:
		Chemical energy is a form of potential energy related to the breaking and forming of chemical bonds.
	www.launchbase.net /encyclopedia/Potential_energy (2046 words)

	POTLIB-online potential energy surface library
		POTLIB-online is a library of global and semiglobal potential energy surface subprograms for calculating Born-Oppenheimer energies as a function of nuclear geometry.
		The goal of the POTLIB project is to facilitate chemical dynamics research by collecting and disseminatng a comprehensive collection of state-of-the-art potential energy routines (developed by a wide, international group of researchers) with systematic and well-defined interfaces for use with chemical dynamics programs.
		If a potential routine from POTLIB-online is used for published work, the publication should give the original reference for the potential that is given at the top of the downloaded files.
	comp.chem.umn.edu /potlib (451 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		We present calculations of fission potential energy surface based on Strutinsky's prescription for realistic 5-parameter shape parametrization of the fissioning nucleus.
		The calculated fission saddle points present typical feature that most of the actinide nuclei have the lowest two saddle points, one is mass-symmetric and the other is mass-asymmetric, separated by a ridge.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20507340 (265 words)

	Potential Energy Maps
		A potential-energy surface is a landscape-like topographical map that describes how the energy of a water cluster varies as individual molecules move.
		An energy minimum occurs whenever any small displacement increases the cluster's overall energy.
		The minimum that's lowest in energy on the potential-energy surface is the global minimum.
	www.psc.edu /science/Jordan/Traversing.html (184 words)

	scanning potential energy surfaces
		In order to cover the relevant part of a potential energy surface, a series of calculations must be performed in which one of the structural parameters is fixed to a certain value, while all other parameters are optimized to their most favorable values.
		Again a summary of the potential energy surface scan is given at the end of the output file containing all geometrical parameters as well as the energy for each of the optimized points.
		Driving a bond angle can also be used to study the potential energy surface of reactions, the isomerization of HCN to CNH being a nice example.
	www.cup.uni-muenchen.de /oc/zipse/lv18099/scan.html (1690 words)

	Two approaches to fitting the potential energy surface
		Abstract: We discuss two distinct approaches to high dimensional interpolation with application to fitting the potential energy surface of small molecules.
		The first approach is reduced Hermite interpolation, which requires, in the cubic case, function values and gradients on the vertices of a box.
		We discuss especially the non-trivial construction of a polynomial basis that respects the symmetry of the potential energy surface under permutations of like nuclei.
	math.nist.gov /mcsd/Seminars/2003/2003-06-18-braams.html (179 words)

	Available fortran and C codes (Site not responding. Last check: 2007-10-30)
		Fortran code #1 for the OHCO potential energy surface (D. Troya et al, J. Phys.
		Fortran code #2 for the OHCO potential energy surface (D. Troya et al, J. Phys.
		Fortran code #3 for the OHCO potential energy surface (D. Troya et al, J. Phys.
	www.chem.northwestern.edu /~schatz/codes/codes.html (123 words)

	Influence of the Intermolecular Potential Energy Surface on Collisional Energy Transfer in the (ResearchIndex)
		Influence of the Intermolecular Potential Energy Surface on Collisional Energy Transfer in the (ResearchIndex)
		Influence of the Intermolecular Potential Energy Surface on Collisional Energy Transfer in the (1998)
		Abstract: Introduction How reactant molecules acquire and lose their energy via collisions is of much relevance to the further development of chemical reaction theory [1].
	citeseer.ist.psu.edu /242950.html (312 words)

	Potential Energy Surface
		We already commented that the magnesium cation stabilizes the transition state removing charge density from the substrate.
		The rest of classical ligands bound to the magnesium cation, including the water, is stable enough to keep its coordination over all our 2 nanosecond simulation.
		) activated at 12 Å at which the smoothing function begins to reduce the potential and eliminated completely at 13 Å.
	klingon.uab.es /prat/Thesis/node104.html (574 words)

	Letter to the Editor
		The experimental data suggest that either the adiabatic electron affinity of CO is markedly lower than the best theoretical values, or the potential energy surface of CO in the vicinity of the surface of the neutral shows a qualitatively different behaviour from what had been predicted.
		Here we present a theoretical study of the CO ground state potential energy surface in the region where the anion is electronically stable, using extended basis sets and highly correlated levels of theory.
		The theoretical results suggest a new way of thinking about electron detachment from metastable CO and have profound implications for the calculation of potential energy surfaces of polar anions.
	stacks.iop.org /0953-4075/36/L127 (305 words)

	Traversing the Potential Energy Surface
		Once a transition state is located, the minima it connects can be found by taking small initial steps away from the stationary point along the eigenvector of the Hessian corresponding to the unique negative eigenvalue (in both the positive and negative directions) and then performing minimizations.
		These authors defined a basin as a set of connected minima that belong to sequences of minima which are monotonically decreasing in energy and which lead down to the lowest energy minimum in the basin.
		If a low rather than a zero temperature is used, the method would be able to escape from shallow basins, whilst not significantly compromising the favourability of downhill moves.
	www-wales.ch.cam.ac.uk /~jon/PhD2/node45.html (743 words)

	A Refined H3 Potential Energy Surface (Site not responding. Last check: 2007-10-30)
		A FORTRAN program which evaluates the new surface and its derivatives is available here.
		The ab initio data to which the new surface is fit are also given.
		Contains 5 files of ground-state ab initio energies, 2 files of non-ab-initio energies that were generated to constrain the surface at short and long range, and the README file above that describes the contents of this archive.
	www.cita.utoronto.ca /~pgmartin/h3pes (346 words)

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