Search found 100 matches

by Neil Drummond
Fri Jan 28, 2022 10:58 am
Forum: The CASINO program
Topic: Stat inefficiency
Replies: 5
Views: 118

Re: Stat inefficiency

The Hartree-Fock nodes in the Be atom can easily be shown to be qualitatively wrong. However, since nodes for most other systems are also qualitatively wrong, I'm not sure why the Be atom should necessarily be so much worse. I'm not sure why you say that backflow between same-spin electrons is usele...
by Neil Drummond
Tue Jan 25, 2022 12:20 pm
Forum: The CASINO program
Topic: Stat inefficiency
Replies: 5
Views: 118

Re: Stat inefficiency

Sorry, the comments about system size are obviously irrelevant in this case. But somewhere in the local energy landscape in configuration space there must have been some feature that led to lots of configuration branching, even though your overall wave function is good. Note that this doesn't invali...
by Neil Drummond
Mon Jan 24, 2022 12:56 pm
Forum: The CASINO program
Topic: Stat inefficiency
Replies: 5
Views: 118

Re: Stat inefficiency

Dear Vladimir, That message means that the rate at which the walkers are branching is comparable with the rate at which they are decorrelating due to propagation in imaginary time. Hence each walker is similar to its sibling walkers (produced in the same branching event). Thus the walkers are not st...
by Neil Drummond
Fri Aug 27, 2021 12:17 pm
Forum: Jobs
Topic: Lecturer in Physics (Condensed Matter Theory)
Replies: 0
Views: 16374

Lecturer in Physics (Condensed Matter Theory)

Lancaster University, United Kingdom Physics Salary: £36,382 to £40,927 Closing Date: Friday 08 October 2021 Interview Date: Thursday 04 November 2021 Reference: A3509 The Department of Physics seeks to appoint a full-time Lecturer to enhance and complement our thriving activities in theoretical co...
by Neil Drummond
Sat Aug 07, 2021 8:50 pm
Forum: Quantum Monte Carlo
Topic: DMC timestep bias asymptotic
Replies: 17
Views: 71005

Re: DMC timestep bias asymptotic

Dear Vladimir, For configuration-by-configuration DMC (in CASINO at least), the effective time step for any particular configuration that has just moved is tau_eff= p .tau, where p is the configuration-move acceptance probability and tau is the real time step. The mean effective time step tau_EFF=<t...
by Neil Drummond
Wed Apr 14, 2021 2:56 pm
Forum: The CASINO program
Topic: backflow issue when C=0
Replies: 7
Views: 21898

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: 14932

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: 9178

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: 9178

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: 16655

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...