Many-Body meets QM/MM: Application to indole in water solution
A. Mosca Conte1E. Ippoliti2, R. Del Sole1, P. Carloni2, O. Pulci1 (1) UNIVERSITA’ DI TOR VERGATA and ETSF (2) SISSA Many Body meets QM/MM: Applications to indole in water solution
Many-Body meets QM/MM: Application to indole in water solution
A. Mosca Conte1
E. Ippoliti2, R. Del Sole1, P. Carloni2, O. Pulci1 (1) UNIVERSITA’ DI TOR VERGATA and ETSF (2) SISSA Many Body meets QM/MM: Applications to indole in water solution
Outline
Many Body meets QM/MM: Applications to indole in water solution Motivations
Methods of calculations
Results
Outline
Many Body meets QM/MM: Applications to indole in water solution Motivations
Methods of calculations
Results
Optical properties of biological systems
Motivations:
Indole is the optically active part of tryptophan
Optical signatures give information on the bio-chemical context surrounding the indole
Solvatocromism
To this end, theoretical simulations are a useful tool
Large scale systems! Indole Many Body meets QM/MM: Applications to indole in water solution
Outline
Many Body meets QM/MM: Applications to indole in water solution Motivations
Methods of calculations
Results
QM simulations:
Electronic properties
Magnetic properties
Optical properties
… MM simulations:
Dynamics
Atomic coord. relaxation
Protein folding
… Advantage:
Computationally less expensive Parametrization of forces and charges: a x q- q+ q+ Fx=h|x-x0|
Fa=b(a-a0) Many Body meets QM/MM: Applications to indole in water solution
QM/MM
QM cell QM MM
(effective charges) q1 q3 q2 Many Body meets QM/MM: Applications to indole in water solution
QM/MM Interface
QM interface MM (eff. Ch.) PCM Link-atoms method: Hybrid-orbital techn.: Pseudo bond approach
Other Many Body meets QM/MM: Applications to indole in water solution
QM
DFT Ground-state properties:
Dynamics, Forces, Bond-lenght Hohenberg and Kohn theorem: Many Body meets QM/MM: Applications to indole in water solution Optical properties TD-DFT MBPT Excited state properties
Optical properties TD-DFT Runge-Gross theorem: PRL (1984) Many Body meets QM/MM: Applications to indole in water solution Linear response: MBPT Absorption spectrum GW +
BSE
(Bethe-Salpter Equation) Energy band excitonic effect vacuum hn hn UNKNOWN
MBPT
GW:
GW/MM: BSE (Bethe-Salpeter Eq.): Many Body meets QM/MM: Applications to indole in water solution
QM/MM
QM cell QM MM
(effective charges) q1 q3 q2 Many Body meets QM/MM: Applications to indole in water solution 2000 H2O molecules
Car-Parrinello dynamics (20 ps)
Environment conditions: 300 K, 1 atm
Optical spectra each 2 ps and average VAPOR PHASE:
Coordinates relaxed in vacuum by Hellman-Feynman forces
All-QM calculation
Outline
Many Body meets QM/MM: Applications to indole in water solution Motivations
Methods of calculations
Results
Car-Parrinello dynamics
Dynamics: 0 20 ps
Time step: 0.1 fs
Absorption spectrum every 2 ps
Convergence of optical spectra with number of snapshots
Independent particle approach (DFT)
6 snapshots are enough! Many Body meets QM/MM: Applications to indole in water solution DFT
Many water molecules required
for optical properties prediction! Many Body meets QM/MM: Applications to indole in water solution How many water molecules do we need for optical spectra of indole in water? Independent particle
approach (DFT)
1 snapshot
Many Body meets QM/MM: Applications to indole in water solution c v hn DFT
DFT Dynamics (20 ps)
Preliminary tests:
Test over the number of snapshots: 6
Test over the number of molcules: 2000 Indipendent particle approach TDDFT or BSE
Optical properties:
Indole in water:
Spectrum obtained by an average over 6 snapshots extracted from previous dynamics and 2000 water molecules
Indole in vapor phase:
Spectrum of indole in vacuum (all-QM calculation) Interacting particles: excitons solvatochromic shift: shift induced by solvent
Solvatocromic shift:
Exp. Value: 0.18 eV
Theor. Values: 0.2 eV (CASPT2: 0.06 eV) Many Body meets QM/MM: Applications to indole in water solution TDDFT GW + BSE
Many Body meets QM/MM: Applications to indole in water solution Solvatochromism: two contributions Vapor phase In water BSE/MM
1 snapshot The solvent shift is a consequence of two effects:
The geometrical distortion
The electrostatic interaction with the solvent
Indole in water with no water field
Dynamics (0 20 ps)
Absorption spectrum at IPA-DFT level every 2 ps.
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