Exploration of some refinements to geometry optimization methods

Birkholz, Adam B.; Schlegel, H. Bernhard

doi:10.1007/s00214-016-1847-3

Cited by 23 publications

(26 citation statements)

References 23 publications

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“…The flowchart method was used for updating model Hessians for quasi-Newton steps. 54 For comparison, the MECIs were also optimized using SA-CASSCF. All of the calculations were performed using the program package bagel.…”

Section: Numerical Examplesmentioning

confidence: 99%

Analytical Derivative Coupling for Multistate CASPT2 Theory

Park

Shiozaki

2017

J. Chem. Theory Comput.

136

169

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The probability of non-radiative transitions in photochemical dynamics is determined by the derivative couplings, the couplings between different electronic states through the nuclear degrees of freedom. Efficient and accurate evaluation of the derivative couplings is, therefore, of central importance to realize reliable computer simulations of photochemical reactions. In this work, the derivative couplings for multistate multireference second-order perturbation theory (MS-CASPT2) and its 'extended' variant (XMS-CASPT2) are studied, in which we present an algorithm for their analytical evaluation. The computational costs for evaluating the derivative couplings are essentially the same as those for calculating the nuclear energy gradients. The geometries and energies calculated with XMS-CASPT2 for small molecules at minimum energy conical intersections (MECIs) are in good agreement with those computed by multireference configuration interaction. As numerical examples, MECIs are optimized using XMS-CASPT2 for stilbene and a GFP model chromophore (the 4-para-hydroxybenzylidene-1,2-dimethyl-imidazolin-5-one anion).

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Section: Numerical Examplesmentioning

confidence: 99%

Analytical Derivative Coupling for Multistate CASPT2 Theory

Park

Shiozaki

2017

J. Chem. Theory Comput.

136

169

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“…If the PES is significantly undulant, conventional minimisation algorithms struggle, as low order spatial derivatives do not suffice in describing the local topology of the potential energy surface. 49 One is frequently reduced to sequentially optimising the system at a number of increasingly complex levels of theory to obtain convergence of the maximum atomic forces and displacements. Whilst tedious, it is also no guarantee of convergence, as we now outline.…”

Section: Weighting and Optimisationmentioning

confidence: 99%

The computational prediction of Raman and ROA spectra of charged histidine tautomers in aqueous solution

Cardamone

Caine

Blanch

et al. 2016

Phys. Chem. Chem. Phys.

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Histidine is a key component of a number of enzymatic mechanisms, and undertakes a myriad of functionalities in biochemical systems. Its computational modelling can be problematic, as its capacity to take on a number of distinct formal charge states, and tautomers thereof, is difficult to capture by conventional techniques. We demonstrate a means for recovering the experimental Raman optical activity (ROA) spectra of histidine to a high degree of accuracy. The resultant concordance between experiment and theory is of particular importance in characterising physically insightful quantities, such as band assignments. We introduce a novel conformer selection scheme that unambiguously parses snapshots from a molecular dynamics trajectory into a smaller conformational ensemble, suitable for reproducing experimental spectra. We show that the "dissimilarity" of the conformers within the resultant ensemble is maximised and representative of the physically relevant regions of molecular conformational space. In addition, we present a conformer optimisation strategy that significantly reduces the computational costs associated with alternative optimisation strategies. This conformer optimisation strategy yields spectra of equivalent quality to those of the aforementioned alternative optimisation strategies. Finally, we demonstrate that microsolvated models of small molecules yield spectra that are comparable in quality to those obtained from ab initio calculations involving a large number of solvent molecules.

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“…Cartesian coordinates are often chosen due to their simple implementation, despite internal coordinates (IC) being superior in many respects: chemical bonds are included as intrinsic coordinates, the curvilinear motion of angle bending or torsions are better represented by internals, and ICs have reduced intercoordinate coupling which allows faster optimization. Further advantages include that the interpolation of a RP in ICs avoids the collision of atoms or intersections of bonds, and ICs can accelerate convergence of optimization by a factor of four …”

Section: Introductionmentioning

confidence: 99%

“…Further advantages include that the interpolation of a RP in ICs avoids the collision of atoms or intersections of bonds, [9,11,12,23,34,54,57,86,99] and ICs can accelerate convergence of optimization by a factor of four. [18,57,58,105] Two common surface-compatible reaction finding methods are the nudged elastic band [62] (NEB) and the dimer [15] method. NEB and its variations [59,60,63,64] interpolate between two structures in Cartesian coordinates to optimize a chain-ofstates representation of the RP.…”

Section: Introductionmentioning

confidence: 99%

Reliable and efficient reaction path and transition state finding for surface reactions with the growing string method

Jafari

Zimmerman

2017

J Comput Chem

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The computational challenge of fast and reliable transition state and reaction path optimization requires new methodological strategies to maintain low cost, high accuracy, and systematic searching capabilities. The growing string method using internal coordinates has proven to be highly effective for the study of molecular, gas phase reactions, but difficulties in choosing a suitable coordinate system for periodic systems has prevented its use for surface chemistry. New developments are therefore needed, and presented herein, to handle surface reactions which include atoms with large coordination numbers that cannot be treated using standard internal coordinates. The double-ended and single-ended growing string methods are implemented using a hybrid coordinate system, then benchmarked for a test set of 43 elementary reactions occurring on surfaces. These results show that the growing string method is at least 45% faster than the widely used climbing image-nudged elastic band method, which also fails to converge in several of the test cases. Additionally, the surface growing string method has a unique single-ended search method which can move outward from an initial structure to find the intermediates, transition states, and reaction paths simultaneously. This powerful explorative feature of single ended-growing string method is demonstrated to uncover, for the first time, the mechanism for atomic layer deposition of TiN on Cu(111) surface. This reaction is found to proceed through multiple hydrogen-transfer and ligand-exchange events, while formation of H-bonds stabilizes intermediates of the reaction. Purging gaseous products out of the reaction environment is the driving force for these reactions. © 2017 Wiley Periodicals, Inc.

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Exploration of some refinements to geometry optimization methods

Cited by 23 publications

References 23 publications

Analytical Derivative Coupling for Multistate CASPT2 Theory

Analytical Derivative Coupling for Multistate CASPT2 Theory

The computational prediction of Raman and ROA spectra of charged histidine tautomers in aqueous solution

Reliable and efficient reaction path and transition state finding for surface reactions with the growing string method

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