{"id":471,"date":"2013-11-24T13:38:59","date_gmt":"2013-11-24T13:38:59","guid":{"rendered":"https:\/\/vallico.net\/casinoqmc\/?p=471"},"modified":"2019-10-09T21:30:27","modified_gmt":"2019-10-09T21:30:27","slug":"qmcitaa8","status":"publish","type":"post","link":"https:\/\/vallico.net\/casinoqmc\/qmcitaa8\/","title":{"rendered":"Report on ‘QMC in the Apuan Alps VIII’ workshop 2013"},"content":{"rendered":"

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\nThe eighth “Quantum Monte Carlo in the Apuan Alps” international workshop took place from the 27th of July to the 3rd of August 2013. The participants spent four hours each morning listening to talks on quantum Monte Carlo and related matters, followed by afternoons of mountain walking, caving, canyoning and other activities.<\/p>\n

The vitality of research in this field was confirmed by the extremely wide variety of applications discussed, which included high-pressure solid hydrogen, rare gas crystals, biomolecules, ultracold atomic gases, water clusters, water-acene complexes, the design of metal alloys, hexagonal boron nitride, point defects in semiconductors and wide-band gap oxides, molecular crystals such as para-diiodobenzene, proton disorder in ice, nanocrystalline alumina, electron-hole systems, the metallization of solid helium, the binding energy of bilayer graphene, correlation-bound anions and organic diradicals, methane binding in ice clathrates, and (for the first time) the high-Tc<\/sub>  superconducting cuprates. Wagner’s talk on this latter subject – in which he showed highly-accurate DMC calculations of the spin-lattice coupling in the real material<\/em> (as opposed to a model system) for the first time – was particularly interesting. He found that some lattice degrees of freedom depended strongly on the magnetic state, and that the spin-lattice coupling was removed with 25% doping. Considerable attention was also paid to computing weak interactions such as van der Waals in QMC; talks by Tkatchenko, Benali, Ambrosetti, Deible, Gillan, Jordan, Mostaani were all devoted to this topic in one or another, and showed the very considerable superiority of QMC results over DFT in this area.  As the power of available computers and the sophistication of the algorithms and software increases, it is clear that the size and complexity of the systems that can be treated within QMC continues to rise rapidly. A number of researchers, including Gillan, Wagner, Maezono, Towler, and Alf\u00e8 are particularly active in pushing the boundaries of what calculations can be done for real systems on large computers.<\/p>\n

A number of more technical questions were addressed. These included forces and correlated sampling, finite-size effects, direct incorporation of light nuclei at the quantum level in DMC calculations, maximum probability domains in crystals, and the use of CASINO on systems containing GPUs. A number of speakers such as Tim Mueller stressed the need for using QMC to generate publically-available databases of highly accurate results – for examples of formation energies – and the subsequent requirement for developing methods for doing ‘high-throughput QMC’. QMC is ideal for such databases – which need only be created once and would be useful for a very long time – not only because it produces highly accurate energetics, but because it scales well with processor
\nnumber and system size and because it works for ‘everything’ (molecules, metals, insulators, semiconductors..). Mueller’s talk had the interesting and surprising conclusion that – given suitable recipes and workflow improvements -‘by 2016-ish we should be able to calculate QMC energies for every known inorganic material on a single supercomputer in (roughly) about a week<\/em>‘.<\/p>\n

A significant number of people in groups in London and Cambridge are involved with stochastic Monte-Carlo approaches to classic quantum chemistry techniques such as CI and coupled cluster, and these efforts were the subject of a number of interesting talks by Spencer, Thom, and Vigor. The FCI-QMC technique can reproduce the results of full CI calculations (for a given finite basis) essentially exactly but in considerably less time, and it is now possible to calculate energies for systems very much larger than was possible before. The stochastic coupled cluster technique discussed by Thom can reproduce large coupled cluster calculations much more quickly; it is considerably simpler to implement than deterministic coupled-cluster, and is feasible on workstations and very parallelizable.<\/p>\n

On a lighter note, notable athletic achievements by the group included the ascents of Monte Matanna, Monte Palodina, Pania della Croce, and Monte Forato, the exploring of the Neanderthal cave (Grotto dell’Onda) and the Cave That Screams, and the penetration of the Turrite di San Rocco and Orrido di Botri canyons. They were the first group to reach the fortress of Trassilico from San Luigi, and ascended a small hill with a nice view near San Pelligrinetto.<\/p>\n

Edgar Engel became the first person since pioneers Evans and Towler to reach the Fat Boy Filter<\/a> in the cave of Cascaltendine by heroically free-climbing the 60 foot wall of the final waterfall chamber. As the opposition fielded their best team (for once) our heroes suffered an embarassing 15-4 hammering by the thrusting young village lads in the fourteenth “Vallico Sotto Against The World” football match (utter humiliation being avoided only by four goals from deadly striker Bartomeu Monserrat-Sanchez). The football was followed by fireworks, dinner, and the Great Rock and Roll Face-off, in which trainee Jerry Lee Lewis impersonator Mike Towler and girly choirboy Alex Thom competed to see who could sing ‘She Was My Baby (He Was My Friend)<\/a>‘ in the least convincing rock’n’roll style. Needless to say, an almost unanimous vote by everyone except his own loyal daughter Saska voted Towler as by far the worst singer. The other days were concluded with evening discussions and dinner, and on Tuesday, by a trip to the Vallico Sopra Festival where the participants ate local delicacies such as necci<\/em>, migliecci<\/em> and pitonca<\/em>, learned how to dance the Moresca, and observed demonstrations of interesting agricultural techniques.<\/p>\n

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