Accuracy of buffered-force QM/MM simulations of silica
- Fraunhofer IWM, Wöhlerstraße 11, 79108 Freiburg (Germany)
- Hybrid Materials Interfaces Group, Faculty of Production Engineering and Bremen Center for Computational Materials Science, University of Bremen, Am Fallturm 1, 28359 Bremen (Germany)
- Department of Physics, King’s College London, Strand, London WC2R 2LS (United Kingdom)
We report comparisons between energy-based quantum mechanics/molecular mechanics (QM/MM) and buffered force-based QM/MM simulations in silica. Local quantities—such as density of states, charges, forces, and geometries—calculated with both QM/MM approaches are compared to the results of full QM simulations. We find the length scale over which forces computed using a finite QM region converge to reference values obtained in full quantum-mechanical calculations is ∼10 Å rather than the ∼5 Å previously reported for covalent materials such as silicon. Electrostatic embedding of the QM region in the surrounding classical point charges gives only a minor contribution to the force convergence. While the energy-based approach provides accurate results in geometry optimizations of point defects, we find that the removal of large force errors at the QM/MM boundary provided by the buffered force-based scheme is necessary for accurate constrained geometry optimizations where Si–O bonds are elongated and for finite-temperature molecular dynamics simulations of crack propagation. Moreover, the buffered approach allows for more flexibility, since special-purpose QM/MM coupling terms that link QM and MM atoms are not required and the region that is treated at the QM level can be adaptively redefined during the course of a dynamical simulation.
- OSTI ID:
- 22416100
- Journal Information:
- Journal of Chemical Physics, Vol. 142, Issue 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ATOMS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CONVERGENCE
COUPLING
COVALENCE
CRACK PROPAGATION
DENSITY OF STATES
FLEXIBILITY
MOLECULAR DYNAMICS METHOD
POINT CHARGE
POINT DEFECTS
QUANTUM MECHANICS
SILICA