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Dear Vladimir, The optimised VMC time step is generally determined by the most important length scale, not necessarily the longest length scale in the system being studied. Fitting a sum of exponential decays to the DMC energy could in principle tell you about excited-state energies. However, these...

I run 1000 equilibration steps 0.01 au each for Be atom with 102400 configurations, split it to 50 groups and plot it with VMC, DMC energies and fits it with exponential an 1/x decay. This test takes 1000 sec for me. 1/x decay fiits better, is it bad news? dmc_equilibration.png Actually it means tha...

Sorry, the time steps should have been 0.001 and 0.00025 a.u. (ratio of 4:1), with populations of 1024 and 4096, respectively (4:1), for optimal efficiency (with twice as many statistics accumulation steps for the smaller time step). The shortest length scale in an all-electron calculation is the B...

Dear Vladimir, All-electron DMC calculations with different Jastrow factors ought to agree exactly (within statistical error bars) in the limit of zero time step, infinite population and with an adequate equilibration period... For an aluminium atom (Z=13) the Bohr radius is 1/13 a.u., suggesting t...

Hello all. I'm going to do the all-electrons calculations of DMC energy of for a set of about 150 molecules сonsisting of atoms from H up to Cl. After obtaining initial molecular orbitals (from ORCA and QCHEM) and performing some JASTROW optimization, I decided to compare how much DMC energy depends...

Hi Vladimir, You should be able to merge the two channels with the rule 1-1=2-2=1-2 , or equivalently 1=2 . Best, Pablo Hi, Pablo. I don't want to merge two channels. I want to exclude 1-1-1-n1 channel, like !n1 exclude first atom or !1-2 excludes 1-1-2-n1 channel in our case. Another possibility t...

Hi CASINO users. I want to checkout contribution for e-e-e-n JASTROW term (in N2). As usual I apply the next rules for: Rules: n1=n2 1-n1=2-n1 1-1=2-2 I have got two different terms 1-1-1-n1 and 1-1-2-n1 but I think that the contribution of the first term is negligible, because the probability of en...

Thank you Ryan, your explanation was very helpful.

Hi all. My question is about correlation.data file. I find detailed explanation about JASTRO factor used for finit system and placed in correlation.data file. https://arxiv.org/pdf/0801.0378.pdf In formulas (19), (20), (21) alpha, beta, gamma have 1, 2 and 4 indexes respectively, but in correlation....

UPD with OO-MP2 orbitals on cc-pCV6Z truncated up to g-orbitals I've got even better result: DMC with dmc_target_weight=2000, dmc_equil_nstep=1000, dmc_stats_nstep=1000000 and dt=0.003 gave me following energies: HF orbitals (cc-pV6Z_truncated) = -40.506027169422 +/- 0.000105457704 OO-MP2 orbitals (...