Interface to DFTD3 by S. Grimme¶
Code author: Lori A. Burns
Section author: Lori A. Burns
Module: Samples
Installation¶
Binary
DFTD3 is available as a conda package for Linux and macOS (and Windows, through the Ubuntu shell).
If using the Psi4conda installer, DFTD3 has already been installed alongside.
If using the PSI4 conda package, the dftd3 conda package can be obtained through
conda install dftd3 c psi4
orconda install psi4rt c psi4
.If using PSI4 built from source, and anaconda or miniconda has already been installed (instructions at Quick Installation), the dftd3 executable can be obtained through
conda install dftd3 c psi4
.To remove a conda installation,
conda remove dftd3
.
Source
If using PSI4 built from source and you want to build DFTD3 from from source also, follow the instructions provided with the source (essentially, download the freely available tarball, unpack the source, edit the Makefile to select a Fortran compiler, and run make). From version 3.1.0 onwards, DFTD3 can be used asis; for earlier versions, patches are available: psi4/psi4/share/psi4/scripts/patch_grimme_dftd3.3.0.2.
To be used by PSI4, the program binary (dftd3
) must be
found in your PSIPATH
or PATH
(in that order). If
PSI4 is unable to execute the binary, an error will be reported.
To preferentially use a particular dftd3 compilation, simply adjust its
position in the path environment variables.
Theory¶
The local or semilocal character of conventional density functionals necessarily leads to neglect of the longrange correlation interactions which capture attractive van der Waals forces. Initially proposed by Yang [Wu:2002:515] and assiduously developed by Grimme, [Grimme:2004:1463] [Grimme:2006:1787] [Grimme:2010:154104] the DFT+Dispersion method appends to the base functional a scaled, damped, and fitted leading term to the wellknown dispersion energy series, \(E_{disp} = C_6/R^6 C_8/R^8 C_{10}/R^{10}\cdots\). The DFTD2 [Grimme:2006:1787] variant takes the explicit form below. Here, dispersion coefficients, \(C_6^{ij}\), obtained from the geometric mean of tabulated elemental values, are summed over interatomic distances, \(R_{ij}\), modulated by a damping function, \(f_{damp}(R_{ij})\), that gradually activates the dispersion correction (at a rate characterized by \(\alpha_6\)) over a distance characterized by the sum of the two atomic vdW radii, \(R_{vdW}\), while an overall scaling term, \(s_6\), is optimized to be unique to each \(E_{xc}\) functional. (\(\alpha_6\) is sometimes allowed to vary as well.)
Grimme recently presented a refined method, DFTD3, [Grimme:2010:154104] which incorporates an additional \(R^{8}\) term in the dispersion series and adjusts the \(C_{6}^{ij}\) combination formula and damping function. The individual atomic \(C_6^i\) are interpolated from several reference values based upon coordination numbers extracted from the molecular structure, rather than assigned solely by atomic identity as in DFTD2, and thereby incorporate some awareness of the chemical environment into an otherwise largely heuristic correction. The D3 dispersion has the following form, where \(s_{r,6}\) and \(s_8\) are the customary nonunity parameters fitted for individual functionals.
A modified damping scheme for DFTD3 using the rational damping form of Becke and Johnson was introduced in [Grimme:2011:1456]. The parameters fit for individual functionals are now \(s_6\), \(s_8\), \(a_1\), and \(a_2\).
All parameters characterizing the dispersion correction are taken from Grimme’s website or else from the literature.
Running DFTD3¶
A number of a posteriori dispersion corrections are available in
PSI4. While some are computed within PSI4‘s codebase (D1, D2,
CHG, DAS2009, DAS2010), the D3 correction and its variants are
available only through the DFTD3
program. Once installed, the
dftd3
/PSI4 interface is transparent, and all corrections are
interfaced exactly alike.
Dispersion corrections are built into DFT functionals, so appending an a
posteriori correction to a computation is as simple as
energy('b2plypd')
vs. energy('b2plyp')
. For example, the
following input file computes (with much redundant work) for water a
B3LYP, a B3LYPD2, and a B3LYPD3 (zerodamping) energy.
molecule h2o {
O
H 1 1.0
H 1 1.0 2 104.5
}
set {
basis ccpVDZ
}
energy('b3lyp')
energy('b3lypd')
energy('b3lypd3')
Consult the table D Functionals to see for each
functional what corrections are available and what default parameters
define them. The dispersion correction is available after a calculation in
the PSI variable DISPERSION CORRECTION ENERGY
.
By default, the output from the dftd3
program is suppressed; to see it in the output file, set print > 2.
Extension 1 
Variant 
Computing Program (engine) 


D D1 D2 D3 D3ZERO D3BJ D3(BJ) D3M D3MZERO D3MBJ D3M(BJ) NL CHG DAS2009 DAS2010 
alias to D2 D1 2 D2 3 alias to D3ZERO D3 4 w/ original zerodamping D3 5 w/ newer BeckeJohnson rational damping alias to D3BJ alias to D3MZERO D3 6 w/ reparameterized and more flexible original zerodamping D3 6 w/ reparameterized newer BeckeJohnson rational damping alias to D3MBJ Grimme’s NL (DFT plus VV10 correlation) 7 Chai & HeadGordon dispersion formula 8 Podeszwa & Szalewicz dispersion formula 9 Podeszwa & Szalewicz dispersion formula 10 
PSI4‘s libdisp
PSI4‘s libdisp OR
PSI4‘s nl PSI4‘s libdisp PSI4‘s libdisp PSI4‘s libdisp 
[\(s_6\)] [\(s_6\), \(\alpha_6\), \(s_{r,6}\)] [\(s_6\), \(s_8\), \(s_{r,6}\), \(\alpha_6\), \(s_{r,8}\)] [\(s_6\), \(s_8\), \(a_1\), \(a_2\)] [\(s_6\), \(s_8\), \(s_{r,6}\), \(\beta\)] [\(s_6\), \(s_8\), \(a_1\), \(a_2\)] [\(b\), \(c\)] via NL_DISPERSION_PARAMETERS [\(s_6\)] [\(s_6\)] [\(s_6\)] 
Footnotes
 1
Note that there are functionals with these extensions (e.g., wB97XD) that, not being Grimme corrections, won’t follow this table exactly.
 2
 3
 4
 5
 6(1,2)
 7
 8
 9
 10
 11
Keyword not used for userdefined functionals where the
dft_dict["dispersion"]["params"]
is easily editable for this purpose. See Advanced Functional Use and Manipulation
A few practical examples:
DFTD2 single point with default parameters (
dftd3
not called)energy('bp86d')
DFTD3BJ optimization with default parameters
optimize('pbed3bj')
DFTD2 optimization with custom s6 parameter
set dft_dispersion_parameters [1.20] optimize('b3lypd2')
DFTD3ZERO single point (b3lyp) with custom s8 parameter (reset all four values)
set dft_dispersion_parameters [1.0, 2.0, 1.261, 14.0] energy('b3lypd3')
DFTD2 single point with
dftd3
instead of PSI4‘s libdispenergy('pbed2', engine='dftd3')
If only dispersion corrections (rather than total energies) are of
interest, the dftd3
program can be run independently of the scf
through the python function run_dftd3()
. (This function
is the same PSI4/dftd3
interface that is called during an scf job.)
This route is much faster than running a DFTD energy.
Some setup:
molecule nene { Ne Ne 1 2.0 } nene.update_geometry()
The same four dispersion corrections/gradients as the section above:
>>> print nene.run_dftd3('bp86', 'd', dertype=0) 7.735e05 >>> E, G = nene.run_dftd3('pbe', 'd3bj') >>> print G [[0.0, 0.0, 1.1809087569358e05], [0.0, 0.0, 1.1809087569358e05]] >>> E, G = nene.run_dftd3('b3lyp', 'd2', {'s6': 1.20}) >>> print E 8.84e05 >>> E, G = nene.run_dftd3(dashlvl='d3', dashparam={'s8': 2.0, 'alpha6': 14.0, 'sr6': 1.261, 's6': 1.0}) >>> print E 0.00024762

qcdb.Molecule.
run_dftd3
(self, func=None, dashlvl=None, dashparam=None, dertype=None, verbose=1)¶ Compute dispersion correction via Grimme’s DFTD3 program.
 Parameters
func (str, optional) – Name of functional (func only, func & disp, or disp only) for which to compute dispersion (e.g., blyp, BLYPD2, blypd3bj, blypd3(bj), hf+d). Any or all parameters initialized from dashcoeff[dashlvl][func] can be overwritten via dashparam.
dashlvl (str, optional) – Name of dispersion correction to be applied (e.g., d, D2, d3(bj), das2010). Must be key in dashcoeff or “alias” or “formal” to one.
dashparam (dict, optional) – Values for the same keys as dashcoeff[dashlvl][‘default’] used to override any or all values initialized by func. Extra parameters will error.
dertype (int or str, optional) – Maximum derivative level at which to run DFTD3. For large molecules, energyonly calculations can be significantly more efficient. Influences return values, see below.
verbose (int, optional) – Amount of printing.
 Returns
energy (float) – When dertype=0, energy [Eh].
gradient (ndarray) – When dertype=1, (nat, 3) gradient [Eh/a0].
(energy, gradient) (tuple of float and ndarray) – When dertype=None, both energy [Eh] and (nat, 3) gradient [Eh/a0].