QMCPACK
MPC correction has gone wrong
When I was conducting the DMC calculation for the supercell of diamond with dimensions 221, I used MPC energy correction. However, I found that the MPC corrected energy was as high as 10 a.u., which is obviously an incorrect result. I tried many methods but still couldn't solve this problem, including increasing the cutoff value. The version of QMCPACK I am using is 3.17.9. Additionally, I also tried the 4.0.1 version of QMCPACK, but the same problem persisted. My input files and calculation results are attached. The input files include pwscf.dmc.in.xml, C.ccECP.xml, pwscf.pwscf.h5, pwscf.ptcl.xml, pwscf.wfs.xml. The output files are named as pwscf.s00*.*
Note some issues reported previously ( #3041 #3251 #5081 ). Are you seeing similar or different behavior from these cases?
Hello, jtkrogel! My question is similar to #5081, which is whether using the MPC correction leads to a significant difference in the final DMC energy. The MPC correction energy is almost always about one-quarter of the total energy. Is this normal? These phenomena also appear in the reference values of the examples in the QMCPACK program, such as in qmcpack-4.0.0/nexus/tests/unit/test_qmcpack_analyzer_files/diamond_twist/vmc/vmc.g003.s000.scalar.dat and qmcpack-4.0.0/tests/solids/diamondC_1x1x1_pp/qmc-ref/qmc_ref_excited.s000.scalar.dat. Another question is whether the MPC correction is directly added to the DMC energy. If so, its impact on the DMC results would be too significant.