1 3
Theor Chem Acc (2015) 134:132
DOI 10.1007/s00214-015-1734-3
REGULAR ARTICLE
A QM/MM program using frozen localized orbitals and the
Huzinaga equation
Bence Hégely
1 · Ferenc Bogár
2 · György G. Ferenczy
3 · Mihály Kállay
1
Received: 23 July 2015 / Accepted: 15 September 2015 / Published online: 16 October 2015
© Springer-Verlag Berlin Heidelberg 2015
appealing HLSCF method is a competitive alternative to
the LA method.
Keywords Mixed quantum mechanics/molecular
mechanics · Huzinaga equation-based local self-consistent
fi eld (HLSCF) · Frozen strictly localized molecular orbital ·
Link atom
1 Introduction
Mixed quantum mechanical/molecular mechanical (QM/
MM) methods are multiscale modeling techniques that
fi nd widespread use in chemistry. The basic idea of QM/
MM methods is that a localized event in a large molecular system is described by a sophisticated computational
method applied explicitly to the central subsystem where
the event takes place, while the effect of the further regions
is taken into account in a more approximate way. Typical
fi elds of application include reaction mechanisms, among
them enzyme-catalyzed biochemical reactions, solvation,
and spectroscopic properties. While QM methods are most
often combined with MM methods, multiscale modeling
also includes the combination of various level QM techniques. An early scheme developed by Náray-Szabó and
Surján [ 1 ] calculates strictly localized molecular orbitals
for the whole system followed by the release of localization for the central subsystem. This QM/QM scheme was
originally developed at the CNDO/2 level and was later
extended to the NDDO level [ 2 ]. A virtue of this method is
that it offers a natural way to separate the central subsystem
and the environment. A strictly localized orbital is the linear
combination of hybrids centered on bound atoms and pointing toward one another. Then atoms at the boundary have
hybrids pointing toward the strictly localized region on the
Abstract A mixed QM/MM computer program coupling
AMBER and MRCC is presented. This is the fi rst implementation of the Huzinaga equation-based local self-consistent
fi eld (HLSCF) method that makes it possible to calculate
ab initio wave functions without orthogonalizing the basis
set to the frozen orbitals separating the QM and MM subsystems. A signifi cant novelty of the program is that it
includes an automatic generation of the frozen localized
orbitals obtained from calculations performed for model
molecules cut out of the system. The AMBER – MRCC code
also allows the use of the link atom (LA) approach. Sample calculations were performed to check the performance
of both the HLSCF and the LA approaches by describing
the interactions between the QM and MM subsystems with
electrostatic embedding. It was found that the conceptually
Published as part of the special collection of articles “Festschrift
in honour of P. R. Surjan”.
Electronic supplementary material The online version of this
article (doi: 10.1007/s00214-015-1734-3 ) contains supplementary
material, which is available to authorized users.
* György G. Ferenczy
ferenczy.gyorgy@ttk.mta.hu
1
MTA-BME Lendület Quantum Chemistry Research Group,
Department of Physical Chemistry and Materials Science ,
Budapest University of Technology and Economics , P.O.
Box 91 , Budapest 1521 , Hungary
2
MTA-SZTE Supramolecular and Nanostructured Materials
Research Group , University of Szeged , Dóm tér 8 ,
Szeged 6720 , Hungary
3
Medicinal Chemistry Research Group, Research Centre
for Natural Sciences , Hungarian Academy of Sciences ,
Magyar Tudósok Körútja 2 , Budapest 1117 , Hungary
133
Reprinted from the journal
Theor Chem Acc (2015) 134:132
DOI 10.1007/s00214-015-1734-3
REGULAR ARTICLE
A QM/MM program using frozen localized orbitals and the
Huzinaga equation
Bence Hégely
1 · Ferenc Bogár
2 · György G. Ferenczy
3 · Mihály Kállay
1
Received: 23 July 2015 / Accepted: 15 September 2015 / Published online: 16 October 2015
© Springer-Verlag Berlin Heidelberg 2015
appealing HLSCF method is a competitive alternative to
the LA method.
Keywords Mixed quantum mechanics/molecular
mechanics · Huzinaga equation-based local self-consistent
fi eld (HLSCF) · Frozen strictly localized molecular orbital ·
Link atom
1 Introduction
Mixed quantum mechanical/molecular mechanical (QM/
MM) methods are multiscale modeling techniques that
fi nd widespread use in chemistry. The basic idea of QM/
MM methods is that a localized event in a large molecular system is described by a sophisticated computational
method applied explicitly to the central subsystem where
the event takes place, while the effect of the further regions
is taken into account in a more approximate way. Typical
fi elds of application include reaction mechanisms, among
them enzyme-catalyzed biochemical reactions, solvation,
and spectroscopic properties. While QM methods are most
often combined with MM methods, multiscale modeling
also includes the combination of various level QM techniques. An early scheme developed by Náray-Szabó and
Surján [ 1 ] calculates strictly localized molecular orbitals
for the whole system followed by the release of localization for the central subsystem. This QM/QM scheme was
originally developed at the CNDO/2 level and was later
extended to the NDDO level [ 2 ]. A virtue of this method is
that it offers a natural way to separate the central subsystem
and the environment. A strictly localized orbital is the linear
combination of hybrids centered on bound atoms and pointing toward one another. Then atoms at the boundary have
hybrids pointing toward the strictly localized region on the
Abstract A mixed QM/MM computer program coupling
AMBER and MRCC is presented. This is the fi rst implementation of the Huzinaga equation-based local self-consistent
fi eld (HLSCF) method that makes it possible to calculate
ab initio wave functions without orthogonalizing the basis
set to the frozen orbitals separating the QM and MM subsystems. A signifi cant novelty of the program is that it
includes an automatic generation of the frozen localized
orbitals obtained from calculations performed for model
molecules cut out of the system. The AMBER – MRCC code
also allows the use of the link atom (LA) approach. Sample calculations were performed to check the performance
of both the HLSCF and the LA approaches by describing
the interactions between the QM and MM subsystems with
electrostatic embedding. It was found that the conceptually
Published as part of the special collection of articles “Festschrift
in honour of P. R. Surjan”.
Electronic supplementary material The online version of this
article (doi: 10.1007/s00214-015-1734-3 ) contains supplementary
material, which is available to authorized users.
* György G. Ferenczy
ferenczy.gyorgy@ttk.mta.hu
1
MTA-BME Lendület Quantum Chemistry Research Group,
Department of Physical Chemistry and Materials Science ,
Budapest University of Technology and Economics , P.O.
Box 91 , Budapest 1521 , Hungary
2
MTA-SZTE Supramolecular and Nanostructured Materials
Research Group , University of Szeged , Dóm tér 8 ,
Szeged 6720 , Hungary
3
Medicinal Chemistry Research Group, Research Centre
for Natural Sciences , Hungarian Academy of Sciences ,
Magyar Tudósok Körútja 2 , Budapest 1117 , Hungary
133
Reprinted from the journal