Stochastic and Deterministic Crystal Structure Solution Methods in GSAS-II: Monte Carlo/Simulated Annealing Versus Charge Flipping

3 Ab initio structure solution by charge flipping

In this paper we present an extremely simple structure solution method termed charge flipping. It works ab initio on high resolution x-ray diffraction data in the manner of Fourier recycling. The real space modification simply changes the sign of charge density below a threshold, while in reciprocal space the modification is the F obs map without any weighting. We test the algorithm using synth...

SUPERFLIP – a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions

SUPERFLIP is a computer program that can solve crystal structures from diffraction data using the recently developed charge-flipping algorithm. It can solve periodic structures, incommensurately modulated structures and quasicrystals from X-ray and neutron diffraction data. Structure solution from powder diffraction data is supported by combining the charge-flipping algorithm with a histogram-m...

Deterministic Annealing for Stochastic Variational Inference

Stochastic variational inference (SVI) maps posterior inference in latent variable models to nonconvex stochastic optimization. While they enable approximate posterior inference for many otherwise intractable models, variational inference methods suffer from local optima. We introduce deterministic annealing for SVI to overcome this issue. We introduce a temperature parameter that deterministic...

Deterministic Versus Stochastic Explanations

Oxygen isotope data for a Pliocene interval from 3.6 to 2.8 million years ago show a mean increase (0.5 per mil) of benthic 6180 at about 3.2 million years ago, whereas planktic 6180 does not increase. This lack of covariance indicates that the event at 3.2 million years did not result in a permanent increase in the ice budget of either the Northern or the Southern Hemisphere. The history of co...

Stochastic versus Deterministic Approaches