Search found 95 matches

by Neil Drummond
Wed Apr 14, 2021 2:56 pm
Forum: The CASINO program
Topic: backflow issue when C=0
Replies: 7
Views: 1877

Re: backflow issue when C=0

Dear Vladimir, Thanks very much for this. As you suggest, replacing if(k>1.and.m<N_phi_eN(set))C(n,p+nphi-1*inc_k+1*inc_m)=-real(m,dp) with if(k>1.and.m<N_phi_ee(set))C(n,p+nphi-1*inc_k+1*inc_m)=-real(m,dp) in pbackflow.f90 should be correct. (I've checked with Pablo.) Sorry about the problem. Best ...
by Neil Drummond
Thu Mar 25, 2021 7:49 pm
Forum: Jobs
Topic: Funded PhD studentship for UK students
Replies: 0
Views: 2279

Funded PhD studentship for UK students

PhD Studentship Quantum Monte Carlo Simulation of Charge Carriers in Two-Dimensional Semiconductors Supervisor Dr Neil Drummond (Department of Physics, Lancaster University, Lancaster, UK) Funded PhD Research Project Applications are invited for a fully-funded PhD research studentship held in the C...
by Neil Drummond
Tue Mar 23, 2021 8:59 am
Forum: The CASINO program
Topic: Problem obtaining static structure factor
Replies: 3
Views: 2366

Re: Problem obtaining static structure factor

Dear Ankush, The structure factor plotted by plot_expval is normalised such that the total structure factor S(k) -> 1 as k->oo, where S(k) = sum_a sum_b S_ab(k), where a and b denote spins. Different normalisation conventions are used in the literature (differing by factors of density N/Omega and ce...
by Neil Drummond
Mon Mar 22, 2021 9:30 pm
Forum: The CASINO program
Topic: Problem obtaining static structure factor
Replies: 3
Views: 2366

Re: Problem obtaining static structure factor

Dear Ankush, Thanks for the question. I was wondering if you could clarify what the problem is? I've just tried running a harmonic wire VMC calculation and I can't see any problem with the static structure factor. I calculated the structure factor by setting structure_factor to T in the input file, ...
by Neil Drummond
Sun May 17, 2020 10:35 am
Forum: The CASINO program
Topic: About dtvmc and PCF
Replies: 1
Views: 10757

Re: About dtvmc and PCF

Dear Ankush, Usually the VMC time step is automatically optimised by choosing it such that the VMC move-acceptance probability is 50%. This is the default behaviour, unless you have set opt_dtvmc to 0 in the input file. If you want to check that your VMC time step is OK, check that the overall accep...
by Neil Drummond
Mon May 04, 2020 3:02 pm
Forum: The CASINO program
Topic: Autotest for cutoffs optimization
Replies: 10
Views: 15283

Re: Autotest for cutoffs optimization

Dear Vladimir & Pablo, You're right: I broke gjastrow optimisation in the patch that Pablo indicated. I've just sent a patch fixing the issue to Mike. Thanks very much for pointing out the problem, and I'm very sorry about the inconvenience. The above results of playing around with the pjastrow ...
by Neil Drummond
Sun May 03, 2020 8:22 am
Forum: The CASINO program
Topic: Autotest for cutoffs optimization
Replies: 10
Views: 15283

Re: Autotest for cutoffs optimization

Dear Vladimir,

The form of Jastrow that you are using is essentially the same that I used: the three terms in your Jastrow factor are u (homogeneous electron-electron), chi (electron-nucleus) and f (electron-electron-nucleus).

Best wishes,

Neil.
by Neil Drummond
Sat May 02, 2020 10:22 pm
Forum: The CASINO program
Topic: Autotest for cutoffs optimization
Replies: 10
Views: 15283

Re: Autotest for cutoffs optimization

Dear Both, Optimisation of cutoff lengths has always been challenging and numerically sensitive. These days I tend to fix the cutoff lengths at sensible values rather than attempt to optimise them. In the present case, fixing L_u=10, L_chi=8 and L_f=7 a.u. works OK: VMC #1: E = -24.588(2) ; var = 0....
by Neil Drummond
Fri May 01, 2020 8:08 pm
Forum: The CASINO program
Topic: Autotest for cutoffs optimization
Replies: 10
Views: 15283

Re: Autotest for cutoffs optimization

Dear Vladimir, Here's a very quick test. For a 27-electron r_s=4 3D electron gas with a Jastrow factor containing a U term only, if I start from a cutoff length of L =4 a.u. and optimise the linear parameters together with the cutoff using variance minimisation: VMC #1: E = -0.0497(1) ; var = 1.30(4...