Properties can be calculated for both the Hartree-Fock and DFT wave functions. The properties that are available are:
- Natural bond analysis
- Dipole, quadrupole, and octupole moment
- Mulliken population analysis and bond order analysis
- Electrostatic potential (diamagnetic shielding) at nuclei
- Electric field and field gradient at nuclei
- Electric field gradients with relativistic effects
- Electron and spin density at nuclei
- NMR shielding (GIAO method)
- NMR hyperfine coupling (Fermi-Contact and Spin-Dipole expectation values)
- NMR indirect spin-spin coupling
- Response to electric and magnetic fields (static and dynamic)
The properties module is started when the task directive TASK
PROPERTY [property keyword] [CENTER ((com || coc || origin || arb <real x y z>) default coc)] END
Most of the properties can be computed for Hartree-Fock (closed-shell RHF, open-shell ROHF, and open-shell UHF), and DFT (closed-shell and open-shell spin unrestricted) wavefunctions. The NMR hyperfine and indirect spin-spin coupling require a UHF or ODFT wave function.
VECTORS [ (<string input_movecs >)]
The VECTORS directive allows the user to specify the input molecular orbital vectors for the property calculation
Each property can be requested by defining one of the following keywords:
NBOFILE DIPOLE QUADRUPOLE OCTUPOLE MULLIKEN ESP EFIELD EFIELDGRAD EFIELDGRADZ4 GSHIFT ELECTRONDENSITY HYPERFINE [<integer> number_of_atoms <integer> atom_list] SHIELDING [<integer> number_of_atoms <integer> atom_list] SPINSPIN [<integer> number_of_pairs <integer> pair_list] RESPONSE [<integer> response_order <real> frequency] AIMFILE MOLDENFILE ALL
ALL keyword generates all currently available properties.
NMR and EPR¶
Both the NMR shielding and spin-spin coupling have additional optional
parameters that can be defined in the input. For the shielding the user
can define the number of atoms for which the shielding tensor should be
calculated, followed by the list of specific atom centers. In the case
of spin-spin coupling the number of atom pairs, followed by the atom
pairs, can be defined (i.e.,
spinspin 1 1 2 will calculate the coupling
for one pair, and the coupling will be between atoms 1 and 2).
For both the NMR spin-spin and hyperfine coupling the isotope that has the highest abundance and has spin, will be chosen for each atom under consideration.
Calculating EPR and paramagnetic NMR parameters¶
The following tutorial illustrates how to combine the hyperfine, gshift and shielding to calculate the EPR and paramagnetic NMR parameters of an open-shell system. All calculations are compatible with the ZORA model potential approach.
NMR: Input Example¶
geometry nocenter C 0.00000000 0.00000000 0.00000000 O 1.18337200 0.00000000 0.00000000 H -.63151821 0.94387462 0.00000000 end basis "*" library 6-311G** end property efieldgradz4 1 3 shielding 2 1 2 hyperfine 2 1 3 gshift end relativistic zora on zora:cutoff_NMR 1d-8 zora:cutoff 1d-30 end dft mult 2 xc becke88 perdew86 end task dft property
CENTER: Center of expansion for multipole calculations¶
The user also has the option to choose the center of expansion for the dipole, quadrupole, and octupole calculations.
[CENTER ((com || coc || origin || arb <real x y z>) default coc)]
com is the center of mass, coc is the center of charge, origin is (0.0, 0.0, 0.0) and arb is any arbitrary point which must be accompanied by the coordinated to be used. Currently the x, y, and z coordinates must be given in the same units as UNITS in GEOMETRY.
Response calculations can be calculated as follows:
property response 1 7.73178E-2 # response order and frequency in Hartree energy units velocity # use modified velocity gauge for electric dipole orbeta # calculate optical rotation 'beta' directly [^4] giao # GIAO optical rotation [^5][^6][^7], forces orbeta bdtensor # calculates B-tilde of Refs. [^5][^7] analysis # analyze response in terms of MOs [^7] damping 0.007 # complex response functions with damping, Ref [^8] convergence 1e-4 # set CPKS convergence criterion (default 1e-4) end
Response calculations are currently supported only for
- order 1 (linear response),
- single frequency,
- electric field,
- mixed electric-magnetic field perturbations.
The output consists of the electric polarizability
and optical rotation tensors (alpha, beta for optical rotation) in
response keyword requires two arguments: response order and frequency in Hartree energy units
aoresponse keyword can be used with same effect as the
giao keywords are absent, the
dipole-length form will be used for the dipole integrals. This is a bit
The isotropic optical rotation is origin independent when using the velocity gauge (by means of
velocity keyword) or with GIAOs 5 (by means of the
With the keyword
fully origin-invariant optical rotation tensor is calculated 57.
orbeta are incompatible.
The input line
set prop:newaoresp 0
outside of the
properties block forces the use of an
older version of the response code, which has fewer features (in
particular, no working GIAO optical rotation) but which has been tested
more thoroughly. In the default newer version you may encounter
undocumented features (bugs).
analysis triggers an analysis of the
response tensors in terms of molecular orbitals.
If the property input block also contains the keyword
pmlocalization, then the analysis is
performed in terms of Pipek-Mezey localized MOs, otherwise the canonical
set is used (this feature may currently not work, please check the sum
of the analysis carefully). See Ref.  for an example. Works with HF
and density functionals for which linear response kernels are
implemented in NWChem.
Raman calculations can be performed by specifying the Raman block. These calculations are performed in conjunction with polarizability calculations. Detailed description of input parameters at https://pubs.acs.org/doi/10.1021/jp411039m#notes-1
RAMAN [ (NORMAL | | RESONANCE) default NORMAL ] [ (LORENTZIAN | | GAUSSIAN) default LORENTZIAN ] [ LOW <double low default 0.0> ] [ HIGH <double high default highest normal mode> ] [ FIRST <integer first default 7> ] [ LAST < integer last default number of normal modes > ] [ WIDTH <double width default 20.0> ] [ DQ <double dq default 0.01> ] END task dft raman
task dft raman numerical
Sample input block:
property response 1 8.8559E-2 damping 0.007 end raman normal lorentzian end
RESONANCE: Type of Raman plot to make.
GAUSSIAN: Generation of smoothed spectra (rather than sticks) using either a Lorentzian function or a Gaussian function. The default is
HIGH: The default range in which to generate the Raman spectrum plot is (0.0, highest wavenumber normal mode) cm-1. The
HIGHkeywords modify the frequency range.
LAST: The default range of indices of normal modes used in the plot is (7, number of normal modes). The
LASTkeywords modify the range of indices.
WIDTH: Controls the width in the smoothed peaks, using Lorentzians or Gaussians, in the plot. The default value for
DQ: Size of the steps along the normal modes. The default value for
DQis 0.01. It is related to the step size dR used in numerical evaluation of polarizability derivative
Raman spectrum in stick format and smoothed using Lorentzians or
Gaussians stored in a filename with format
The number of points is 1000 by default. This value can be changed by adding the following SET directive to the input file
set raman:numpts <integer>
Polarizability computed with the Sum over Orbitals method¶
As an alternative to the linear response method, the Sum over Orbitals (SOO) method is available to compute polarizabilities. Results of these method are much less accurate than linear response calculations, with values off by a factor of 2-4x. However, the qualitative nature of this results can be used to compute Raman frequencies when coupled with QMD, as described in references 1213.
Sample input computing polarizability both with the SOO method and the linear response method:
property polfromsos end task dft property property response 1 0 end task dft property
NBOFILE does not execute the Natural Bond Analysis code, but
simply creates an input file to be used as input to the stand-alone NBO
code. All other properties are calculated upon request.
Following the successful completion of an electronic structure
calculation, a Natural Bond Orbital (NBO) analysis may be carried out by
providing the keyword
NBOFILE in the
PROPERTY directive. NWChem will
query the rtdb and construct an ASCII file, file_prefix
.gen, that may
be used as input to the stand alone version of the NBO program, GenNBO.
file_prefix is equal to string following the
START directive. The
input deck may be edited to provide additional options to the NBO
calculation, (see the NBO user’s manual for details.)
Users that have their own NBO version can compile and link the code into the NWChem software. See the INSTALL file in the source for details.
Gaussian Cube Files¶
Electrostatic potential (keyword
esp) and the magnitude of the
electric field (keyword
efield) on the grid can be generated in the
form of the Gaussian Cube File. This behavior is triggered by the
inclusion of grid keyword as shown
grid [pad dx [dy dz]] [rmax x y z] [rmin x y z] [ngrid nx [ny nz]] [output filename]
pad dx [dy dz]- specifies amount of padding (in angstroms) in x,y, and z dimensions that will be applied in the automatic construction of the rectangular grid volume based on the geometry of the system. If only one number is provided then the same amount of padding will be applied in all dimensions. The default setting is 4 angstrom padding in all dimensions.
rmin x y z- specifies the coordinates (in angstroms) of the minimum corner of the rectangular grid volume. This will override any padding in this direction.
rmax x y z- specifies the coordinates (in angstroms) of the maximum corner of the rectangular grid volume. This will override any padding in this direction.
ngrid nx [ny nz]- specifies number of grid points along each dimension. If only one number is provided then the same number of grid points are assumed all dimensions. In the absence of this directive the number of grid points would be computed such that grid spacing will be close to 0.2 angstrom, but not exceeding 50 grid points in either dimension.
output filename- specifies name of the output cube file. The default behavior is to use prefix
-elf.cubefile names for electrostatic potential or electric field respectively. Here prefix denotes the system name as specified in start directive. Note that Gaussian cube files will be written in the run directory (where the input file resides).
Example input file
echo start nacl geometry nocenter noautoz noautosym Na -0.00000000 0.00000000 -0.70428494 Cl 0.00000000 -0.00000000 1.70428494 end basis * library 6-31g* end #electric field would be written out to nacl.elf.cube file #with #ngrid : 20 20 20 #rmax : 4.000 4.000 5.704 #rmin :-4.000 -4.000 -4.704 property efield grid pad 4.0 ngrid 20 end task dft property #electrostatic potential would be written to esp-pad.cube file # with the same parameters as above property esp grid pad 4.0 ngrid 20 output esp-pad.cube end task dft property #illustrating explicit specification of minumum box coordinates property esp grid pad 4.0 rmax 4.000 4.000 5.704 ngrid 20 end task dft property
This keyword generates AIM Wavefunction files. The resulting AIM wavefunction file (.wfn/.wfx) can be post-processed with a variety of codes, e.g.
WARNING: Since we have discovered issues in generating .WFN files with this module (e.g. systems with ECPs), the recommended method for generating .WFN file is to first generate a Molden file with the Moldenfile option, then convert the Molden file into a WFN file by using the Molden2AIM program.
MOLDENFILE MOLDEN_NORM (JANPA | | NWCHEM || NONE)
This keyword generates files using the Molden format. The resulting Molden file (.molden) should compatible with a variety of codes that can input Molden files, e.g.
- JANPA (the nwchem2molden step is no longer
required when using .molden files and the
MOLDEN_NORM option allows the renormalization of the basis set
coefficients. By default, the coefficient values from input are not
modified. Using the
JANPA value coefficients are normalized following
convention (where basis coefficients are normalized to unity), while the
NWCHEM will produce coefficients normalized
according to NWChem’s convention. Using
leave the input coefficients unmodified.
It is strongly recommended to use spherical basis set when using the NWChem Molden output for JANPA analysis
Example input file for a scf calculation. The resulting Molden file will
start heat geometry; he 0. 0. 0.; end basis spherical; * library 6-31g ; end task scf property vectors heat.movecs moldenfile molden_norm janpa end task scf property
Then, the resulting
h2o.molden file can be post processed by Janpa with the following command
java -jar janpa.jar h2o.molden > h2o.janpa.txt
Localized molecular orbitals can be computed with the
localization (( pm || boys || ibo) default pm)
The following methods are available:
Autschbach, J.; Patchkovskii, S.; Pritchard, B. Calculation of Hyperfine Tensors and Paramagnetic NMR Shifts Using the Relativistic Zeroth-Order Regular Approximation and Density Functional Theory. Journal of Chemical Theory and Computation 2011, 7 (7), 2175–2188. https://doi.org/10.1021/ct200143w. ↩
Aquino, F.; Pritchard, B.; Autschbach, J. Scalar Relativistic Computations and Localized Orbital Analyses of Nuclear Hyperfine Coupling and Paramagnetic NMR Chemical Shifts. Journal of Chemical Theory and Computation 2012, 8 (2), 598–609. https://doi.org/10.1021/ct2008507. ↩
Aquino, F.; Govind, N.; Autschbach, J. Scalar Relativistic Computations of Nuclear Magnetic Shielding and <i>g</i>-Shifts with the Zeroth-Order Regular Approximation and Range-Separated Hybrid Density Functionals. Journal of Chemical Theory and Computation 2011, 7 (10), 3278–3292. https://doi.org/10.1021/ct200408j. ↩
Autschbach, J. Time-Dependent Density Functional Theory for Calculating Origin-Independent Optical Rotation and Rotatory Strength Tensors. ChemPhysChem 2011, 12 (17), 3224–3235. https://doi.org/10.1002/cphc.201100225. ↩↩↩
Krykunov, M.; Autschbach, J. Calculation of Optical Rotation with Time-Periodic Magnetic-Field-Dependent Basis Functions in Approximate Time-Dependent Density-Functional Theory. The Journal of Chemical Physics 2005, 123 (11), 114103. https://doi.org/10.1063/1.2032428. ↩
Moore, B.; Srebro, M.; Autschbach, J. Analysis of Optical Activity in Terms of Bonds and Lone-Pairs: The Exceptionally Large Optical Rotation of Norbornenone. Journal of Chemical Theory and Computation 2012, 8 (11), 4336–4346. https://doi.org/10.1021/ct300839y. ↩↩
Krykunov, M.; Kundrat, M. D.; Autschbach, J. Calculation of Circular Dichroism Spectra from Optical Rotatory Dispersion, and Vice Versa, as Complementary Tools for Theoretical Studies of Optical Activity Using Time-Dependent Density Functional Theory. The Journal of Chemical Physics 2006, 125 (19), 194110. https://doi.org/10.1063/1.2363372. ↩
Hammond, J. R.; Govind, N.; Kowalski, K.; Autschbach, J.; Xantheas, S. S. Accurate Dipole Polarizabilities for Water Clusters n=212 at the Coupled-Cluster Level of Theory and Benchmarking of Various Density Functionals. The Journal of Chemical Physics 2009, 131 (21), 214103. https://doi.org/10.1063/1.3263604. ↩
Mullin, J. M.; Autschbach, J.; Schatz, G. C. Time-Dependent Density Functional Methods for Surface Enhanced Raman Scattering (SERS) Studies. Computational and Theoretical Chemistry 2012, 987, 32–41. https://doi.org/10.1016/j.comptc.2011.08.027. ↩
Aquino, F. W.; Schatz, G. C. Time-Dependent Density Functional Methods for Raman Spectra in Open-Shell Systems. The Journal of Physical Chemistry A 2014, 118 (2), 517–525. https://doi.org/10.1021/jp411039m. ↩
Fischer, S. A.; Ueltschi, T. W.; El-Khoury, P. Z.; Mifflin, A. L.; Hess, W. P.; Wang, H.-F.; Cramer, C. J.; Govind, N. Infrared and Raman Spectroscopy from Ab Initio Molecular Dynamics and Static Normal Mode Analysis: The C-H Region of DMSO as a Case Study. The Journal of Physical Chemistry B 2015, 120 (8), 1429–1436. https://doi.org/10.1021/acs.jpcb.5b03323. ↩
Aprà, E.; Bhattarai, A.; Baxter, E.; Wang, S.; Johnson, G. E.; Govind, N.; El-Khoury, P. Z. Simplified Ab Initio Molecular Dynamics-Based Raman Spectral Simulations. Applied Spectroscopy 2020, 74 (11), 1350–1357. https://doi.org/10.1177/0003702820923392. ↩
Pipek, J.; Mezey, P. G. A Fast Intrinsic Localization Procedure Applicable for Ab Initio and Semiempirical Linear Combination of Atomic Orbital Wave Functions. The Journal of Chemical Physics 1989, 90 (9), 4916–4926. https://doi.org/10.1063/1.456588. ↩
Knizia, G. Intrinsic Atomic Orbitals: An Unbiased Bridge Between Quantum Theory and Chemical Concepts. Journal of Chemical Theory and Computation 2013, 9 (11), 4834–4843. https://doi.org/10.1021/ct400687b. ↩
Knizia, G.; Klein, J. E. M. N. Electron Flow in Reaction Mechanisms-Revealed from First Principles. Angewandte Chemie International Edition 2015, 54 (18), 5518–5522. https://doi.org/10.1002/anie.201410637. ↩