dmrg-scf module (maquis-molcas … · brief overview of mcscf/casscf/dmrgscf ... the...
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REFERENCES
[1] L. W. Chung, S. Hayashi, M. Lundberg, T. Nakatsu, H. Kato, and K. Morokuma, J. Am. Chem. Soc. 2008,
130, 12880-12881.
[2] I. Navizet, Y.-J. Liu, N. Ferré, D. Roca-Sanjuán, and R. Lindh, ChemPhysChem, 2011, 12, 3064-3076.
[3] Y. Ma, S. Knecht, S. Keller, R. Lindh, and M. Reiher, in preparation.
[4] T. Dresselhaus, J. Neugebauer, S. Knecht, S. Keller, Y. Ma, and M. Reiher, J. Chem. Phys., 2015, 142, 044111.
[5] G. Barcza, Ö. Legeza, K. H. Marti, and M. Reiher, Phys. Rev. A, 2011, 83, 012508.
[6] K. Boguslawski, K. H. Marti, and M. Reiher, J. Chem. Phys., 2011, 134, 224101.
EXAMPLE: GEOMETRY OPTIMIZATIONS
Since the gradients can be obtained readily, the geom-
etry optimization using DMRG-SCF could be carried
out.
The same optimized minimum geometries of n → σ∗state and σ → σ∗ state can be obtained when compar-
ing to those of CASSCF results:
σ → σ∗
n→ σ∗
Additionally, the transition state (TS) and conical in-
tersection point could also be determined, e.g.
Figure : Optimized TS(O-O) (left) and CI(C-C) (right) structures
* Larger active space results are currently under con-
sideration.
EXAMPLE: DMRG-IN-DFT EMBEDDING
The DMRG-in-DFT embedding may facilitate accu-
rate calculations on systems with strong static corre-
lation embedded in environments whose effects are
important beyond a classical description.
Table: Dipole moment µ in Debye from DMRG-in-
DFT calculations
ENTANGLEMENT AND EXCITATION ANALYSIS
The single-orbital entropy s(1)i [5], which can be un-
derstood as a measure of the interaction of one orbital
with all other orbitals,
s(1)i = −∑α
wα,i ln wα,i
two-orbital entropy s(2)i,j [5],
s(2)i,j = −∑α
wα,i,j ln wα,i,j
and mutual information Ii,j [5], which measure the en-
tanglement between different orbitals,
Ii,j = 12(s(2)i,j − s(1)i − s(2)j)(1− δi,j)
are all supported.
The sampling-reconstruction complete active space
(SR-CAS) algorithm [6] is also supported. It allows
the character of an electronic state can be analyzed
using the Slater-determinant (SD) language.
CONCLUSION
DMRG-SCF calculations are now possible in the
MAQUIS-MOLCAS environment developed by us.
The FDE scheme is used with a freeze-and-thaw strat-
egy to consider the environment effects. Entangle-
ment and excitation analyses are also supported in or-
der to investigate the nature of electronic correlations
in the studied systems.
DMRG EMBEDDED IN QUANTUM ENVIRONMENT
The DMRG calculations can be embedded in an en-
vironment described by density functional theory [4].
The frozen density embedding (FDE) scheme is used
with a freeze-and-thaw strategy for a self-consistent
polarization of the orbital-optimized wavefunction
and the environmental densities.
THE GRADIENT OF A DMRG-SCF STATE
The orbital Lagrangian in this case is symmetric and
thus the calculation of the energy gradient can be di-
rectly deduced based on the Hellmann-Feynman theo-
rem,
g = ∂E
∂r= ∂〈Ψ|H|Ψ〉
∂r= 〈Ψ|H
∂r|Ψ〉
Thus, it is straightforward in the state-specific case.
For the state-averaged case, however, further treat-
ment needs to be considered and currently an approx-
imate but efficient way has been implemented in our
MAQUIS-MOLCAS interface [3].
BRIEF OVERVIEW OF MCSCF/CASSCF/DMRGSCF
The DMRG-SCF wave function contains the matrix-
product states (MPS) as well as the orbital rotation
parameter eR,
The orbital-optimization process is based on a series
of unitary transformations, in which the exponential
expansion of orbital rotation matrix R is involved,
BACKGROUND
Theoretical treatment of chemical reactions involving
excited electronic states has been a challenging prob-
lem for a long time. Photochemical systems such as
the bioluminescent have received significant compu-
tational attention [1, 2].
In order to give a reliable description of the above-
mentioned bioluminescence process, many degener-
ated electronic states should be calculated simultane-
ously with in a multi-configurational (MC) ansatz.
Considering that the DMRG algorithm can handle
much larger active orbital spaces than that of tradi-
tional MC methods, DMRG is a suitable alternative.
DMRG-SCF MODULE (MAQUIS-MOLCAS INTERFACE) IN MOLCASWITH APPLICATION TO SIMPLIFIED BIOLUMINESCENCE MODEL
Yingjin Ma1, Stefan Knecht1, Sebastian Keller1, Roland Lindh2,and Markus Reiher1
1Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich,Switzerland
Email: {yingjin.ma, stefan.knecht, sebastian.keller, markus.reiher}@phys.chem.ethz.ch2 Department of Chemistry - Ångström, POB 518, SE-751 20 Uppsala, Sweden
Email: [email protected]