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CATEGORIES:Electronic Structure Discussion Group
SUMMARY:Recent progress in the first-principles quantum Mo
nte Carlo: New algorithms in the all-electron calc
ulations and a workflow system for QMC optimizatio
ns - Kosuke Nakano
DTSTART;TZID=Europe/London:20190904T113000
DTEND;TZID=Europe/London:20190904T123000
UID:TALK128785AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/128785
DESCRIPTION:First-principles quantum Monte Carlo (QMC) techniq
ues\, such as variational quantum Monte Carlo (VMC
) and diffusion quantum Monte Carlo (DMC)\, are am
ong the state-of-the-art numerical methods used to
obtain highly accurate many-body wave functions.
These methods are especially useful when tackling
challenging cases such as low-dimensional material
s[1] because QMC is no longer dependent on any sem
i-empirical exchange-correlation functions. We hav
e been intensively improving a QMC code "TurboRVB\
," which has been mainly developed by Prof. Sandro
Sorella (SISSA)[2]. I am going to talk about two
recent improvements in the QMC algorithm.\n\nThe f
irst topic is about all-electron calculations. Alt
hough it is convenient to replace core electrons i
n QMC calculations as in DFT\, such replacement so
metimes induces nontrivial biases. All-electron ca
lculations in QMC are not as widely used as in DFT
because the computational cost scales with Z^5.5−
6.5\, where Z is the atomic number. We have recent
ly developed new algorithms to drastically decreas
e computational costs of all-electron DFT (valid o
nly for QMC)[3]\, and all-electron lattice regular
ized diffusion monte Carlo (LRDMC)[4\,5]. I will p
resent basic ideas of the new algorithms and show
several applications such as a binding energy calc
ulation of the sodium dimer[3]. \n\nThe second top
ic is about a workflow system for QMC optimization
s. We are currently developing a python wrapper fo
r TurboRVB\, which is called Genius-TurboRVB (g-tu
rbo)\, in order to "automatize" the complicated op
timization procedure of a many-body wave function.
The wrapper also makes it much easier to prepare
input files\, to analyze output files\, and to per
form advanced calculations. I will present fundame
ntal features and several applications of the wrap
per\, for example\, a phonon dispersion calculatio
n of a solid[6].\n\n[1] S. Sorella\, et al. Phys.
Rev. Lett. 121\, 066402 (2018).\n\n[2] S. Sorella\
, https://people.sissa.it/~sorella/web\, accessed
4 August (2019).\n\n[3] K. Nakano\, et al. J. Chem
. Theory Comput. 15\, 4044-4055 (2019).\n\n[4] M.
Casula\, et al. Phys. Rev. Lett. 95\, 100201 (2005
).\n\n[5] K. Nakano\, et al. to be submitted to Ph
ys. Rev. Lett.\n\n[6] K. Nakano\, et al. in prepar
ation.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
CONTACT:Angela Harper
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