The Nuclear-Electronic Orbital (NEO) Method
Developed by the group of Sharon Hammes-Schiffer at
The Pennsylvania State University, University Park, PA
Coded by Simon P. Webb, Tzvetelin Iordanov, Mike Pak,
Chet Swalina, and Jonathan Skone
The NEO approach is designed to incorporate nuclear quantum effects into
electronic structure calculations by treating specified nuclei quantum
mechanically on the same level as the electrons. The basic objective of
this method is the solution of a mixed nuclear-electronic timeindependent
Schrödinger equation with molecular orbital methods. Both electronic and
nuclear molecular orbitals are expressed as linear combinations of
Gaussian
basis functions. The variational method is used to minimize the energy
with
respect to all molecular orbitals, as well as the centers of the nuclear
basis
functions. Significant correlation effects among electrons and nuclei
are
included with multiconfigurational and perturbation theory methods. This
approach is particularly useful for the description of hydrogen transfer
and
hydrogen bonding. For these applications, the hydrogen nuclei, as well
as all
electrons, are treated quantum mechanically.
The current version of the NEO program in GAMESS includes the NEO-HF
(Hartree-Fock) and NEO-MP2 (second-order many-body perturbation theory)
energies, as well as the NEO configuration interaction (NEO-CI),
NEO multiconfigurational self-consistent field (NEO-MCSCF), NEO
nonorthogonal configuration interaction (NEO-NCI), and NEO electronelectron
correlation density functional theory (NEO-DFT(ee)) energies.
Analytical NEO-HF gradients can be used to optimize the positions of the
classical nuclei and the quantum nuclear basis function centers.
NEO-HF numerical Hessians are also available.
Any problems, bugs, and suggestions should be directed to Prof. Sharon
Hammes-Schiffer (shs@chem.psu.edu).
Users of the NEO program are requested to cite the first NEO paper:
S. P. Webb, T. Iordanov, and S. Hammes-Schiffer, J. Chem. Phys. 117,
4106-4118
(2002).
Users of the NEO-MP2 method are requested to cite the first
NEO-MP2 paper:
C. Swalina, M. V. Pak, and S. Hammes-Schiffer, Chem. Phys. Lett. 404,
394-399 (2005).
Users of the NEO-NCI method are requested to cite the NEO-NCI paper:
J. H. Skone, M. V. Pak, and S. Hammes-Schiffer, J. Chem. Phys.
123, 134108 (2005).
NEO References
1. S. P. Webb, T. Iordanov, and S. Hammes-Schiffer,
Multiconfigurational
nuclear-electronic orbital approach: Incorporation of nuclear quantum
effects
in electronic structure calculations, J. Chem. Phys. 117, 4106-4118
(2002).
2. T. Iordanov and S. Hammes-Schiffer, Vibrational analysis for the
nuclear-electronic orbital method, J. Chem. Phys. 118, 9489-9496 (2003).
3. M. V. Pak and S. Hammes-Schiffer, Electron-proton correlation for
hydrogen tunneling systems, Phys. Rev. Lett. 92, 103002 (2004).
4. M. V. Pak, C. Swalina, S. P. Webb, and S. Hammes-Schiffer,
Application
of the nuclear-electronic orbital method to hydrogen transfer systems:
Multiple centers and multiconfigurational wavefunctions, Chemical Physics
304,
227-236 (2004).
5. C. Swalina, M. V. Pak, and S. Hammes-Schiffer, Alternative
formulation
of many-body perturbation theory for electron-proton correlation,
Chem. Phys. Lett. 404, 394-399 (2005).
6. C. Swalina, M. V. Pak, and S. Hammes-Schiffer, Analysis of the
nuclear-electronic orbital method for model hydrogen transfer systems,
J. Chem. Phys. 123, 014303 (2005).
7. Reyes, M. V. Pak, and S. Hammes-Schiffer, Investigation of isotope
effects with the nuclear-electronic orbital approach, J. Chem. Phys. 123,
064104 (2005).
8. J. H. Skone, M. V. Pak, and S. Hammes-Schiffer, Nuclear-electronic
orbital nonorthogonal configuration interaction approach, J. Chem. Phys.
123, 134108 (2005).
9. C. Swalina and S. Hammes-Schiffer, Impact of nuclear quantum
effects
on the molecular structure of bihalides and the hydrogen fluoride dimer,
J. Phys. Chem. A 109, 10410-10417 (2005).
10. C. Swalina, M. V. Pak, A. Chakraborty, and S. Hammes-Schiffer,
Explicit dynamical electron-proton correlation in the nuclear-electronic
orbital framework, J. Phys. Chem. A 110, 9983-9987 (2006).
11. M. V. Pak, A. Chakraborty, and S. Hammes-Schiffer, Density
Functional
Theory Treatment of Electron Correlation in the Nuclear-Electronic
Orbital
Approach, J. Phys. Chem. A 111, 4522-4526 (2007).
12. M. K. Ludlow, J. H. Skone, and S. Hammes-Schiffer, Substituent
Effects
on the Vibronic Coupling for the Phenoxyl/Phenol Self-Exchange Reaction,
J. Phys. Chem. B (in press).
Notes for NEO programmers.
The NEO code follows the programming conventions outlined in Section 5 of
the GAMESS manual. Further, for the sake of managable maintenance, the
NEO
code has a clean and simple interface with the regular GAMESS code, which
consists of the minimum possible NEO calls and variables appearing in the
regular GAMESS source modules. All added NEO code should likewise
encroach
as little as possible on the regular GAMESS source code.
Names of source code modules (found in ../gamess/qmnuc/neo)
Module
-----NEO
NEOBAS
NEOCAS
NEODEN
NEOFCI
NEOHF
NEOINT
NEOMP2
NEONCI
NEOPRP
NEOSYM
NEOTRN
Description
----------Reads NEO input and sets up NEO calculations
NEO basis sets
Routines needed for orbital updates in NEO-MCSCF
NEO-CI 1 and 2 particle denisty matrices
NEO determinant full configuration interaction
NEO Hartree-Fock
NEO nuclear-electron and nuclear-nuclear integrals
NEO 2nd Moller-Plesset
NEO nonorthogonal configuration interaction
Nuclear property analysis
Symmetry code for NEO orbitals
Transformation of NEO integrals from AO to MO
Disk Files used by the NEO code.
Unit Name
------30
DAFL30
67
ELNUINT
68
NUNUINT
69
NUMOIN
70
NUMOCAS
integrals
Contents
-------Nuclear DIIS in NEO-HF
Nuclear-electronic integrals
Nuclear-nuclear integrals
Nuclear-nuclear MO integrals
Nuclear-electronic partially transformed
71
NUELMO
72
NUELCAS
integrals
Nuclear-electronic MO integrals
Nuclear-electronic partially transformed
Direct Access Files used by the NEO code.
440. 1-nucleus core Hamiltonian matrix
441. QM-nuclei overlap matrix
442. nuclear kinetic energy integrals
443. NEO symmetry adapted Q matrix
444. NEO nuclear molecular orbitals (PMOs)
445. NEO QM-nuclear density matrix
446. NEO Fock matrix
447. Nuclear orbital energies
448. Electron - QM-nuclear contribution to Fock matrix
449. QM nuclear-nuclear contribution to Fock matrix
450. Alpha electron Fock-matrix during NEO-HF
451. Beta electron Fock-matrix during NEO-HF
452. SALC matrix for NEO nuclear orbitals
453. nuclear molecular orbital irreps
454. 1-electron density in MO basis
455.
456. 1-nucleus (proton) density in MO basis
457. 2-nucleus (proton) density in MO basis
458. electron-nuclear mixed density in MO basis
459. 1-nuclues core Hamiltonian in the MO basis.
460. modification to 1-nuclear MOs due to electronic frozen core
461.
462. Cartesian atomic coordinates of vib0 structure (used during
hessian)
463. Force constant matrix during NEO hessian
464. x nuclear dipole integrals, in AO basis
465. y nuclear dipole integrals, in AO basis
466. z nuclear dipole integrals, in AO basis
Standard GAMESS documentation reserves 440-469 for NEO,
please inform Mike Schmidt if NEO ever needs to use
something outside this range.