All computations performed with MOLPRO using default options unless otherwise specified. ------ Table S1. Cartesian coordinates and total energies of the S trimer C 1.391507 0.000000 -3.800020 C -1.391507 0.000000 -3.800020 C 1.391507 0.000000 3.800020 C -1.391507 0.000000 3.800020 C 0.695754 1.205081 -3.800020 C -0.695754 1.205081 -3.800020 C -0.695754 -1.205081 -3.800020 C 0.695754 -1.205081 -3.800020 C 0.695754 -1.205081 3.800020 C -0.695754 -1.205081 3.800020 C -0.695754 1.205081 3.800020 C 0.695754 1.205081 3.800020 C 1.391507 0.000000 0.000000 C -1.391507 0.000000 0.000000 C 0.695754 -1.205081 0.000000 C -0.695754 -1.205081 0.000000 C -0.695754 1.205081 0.000000 C 0.695754 1.205081 0.000000 H 2.471513 0.000000 -3.800020 H -2.471513 0.000000 -3.800020 H 2.471513 0.000000 3.800020 H -2.471513 0.000000 3.800020 H 1.235756 2.140393 -3.800020 H -1.235756 2.140393 -3.800020 H -1.235756 -2.140393 -3.800020 H 1.235756 -2.140393 -3.800020 H 1.235756 -2.140393 3.800020 H -1.235756 -2.140393 3.800020 H -1.235756 2.140393 3.800020 H 1.235756 2.140393 3.800020 H 2.471513 0.000000 0.000000 H -2.471513 0.000000 0.000000 H 1.235756 -2.140393 0.000000 H -1.235756 -2.140393 0.000000 H -1.235756 2.140393 0.000000 H 1.235756 2.140393 0.000000 CCSD(T)/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.16361048 MP2 total energy: -694.54986818 !CCSD(T) ENERGY -694.770132675357 ------ Table S2. Cartesian coordinates and total energies of the T1 trimer C -5.000026 0.000000 1.391507 C -5.000026 0.000000 -1.391507 C 5.000026 0.000000 1.391507 C 5.000026 0.000000 -1.391507 C -5.000026 -1.205081 0.695754 C -5.000026 -1.205081 -0.695754 C -5.000026 1.205081 -0.695754 C -5.000026 1.205081 0.695754 C 5.000026 1.205081 0.695754 C 5.000026 1.205081 -0.695754 C 5.000026 -1.205081 -0.695754 C 5.000026 -1.205081 0.695754 C -1.391507 0.000000 0.000000 C 1.391507 0.000000 0.000000 C -0.695754 -1.205081 0.000000 C 0.695754 -1.205081 0.000000 C 0.695754 1.205081 0.000000 C -0.695754 1.205081 0.000000 H -5.000026 0.000000 2.471513 H -5.000026 0.000000 -2.471513 H 5.000026 0.000000 2.471513 H 5.000026 0.000000 -2.471513 H -5.000026 -2.140393 1.235756 H -5.000026 -2.140393 -1.235756 H -5.000026 2.140393 -1.235756 H -5.000026 2.140393 1.235756 H 5.000026 2.140393 1.235756 H 5.000026 2.140393 -1.235756 H 5.000026 -2.140393 -1.235756 H 5.000026 -2.140393 1.235756 H -2.471513 0.000000 0.000000 H 2.471513 0.000000 0.000000 H -1.235756 -2.140393 0.000000 H 1.235756 -2.140393 0.000000 H 1.235756 2.140393 0.000000 H -1.235756 2.140393 0.000000 CCSD(T)/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.17458434 MP2 total energy: -694.55149111 !CCSD(T) ENERGY -694.773979377540 ------ Table S3. Cartesian coordinates and total energies of the T2 trimer C 0.000000 0.000000 1.391507 C 0.000000 0.000000 -1.391507 C 0.000000 -1.205081 0.695754 C 0.000000 -1.205081 -0.695754 C 0.000000 1.205081 -0.695754 C 0.000000 1.205081 0.695754 C 3.608519 0.000000 0.000000 C -3.608519 0.000000 0.000000 C 4.304272 -1.205081 0.000000 C 4.304272 1.205081 0.000000 C -4.304272 1.205081 0.000000 C -4.304272 -1.205081 0.000000 C 5.695780 -1.205081 0.000000 C 5.695780 1.205081 0.000000 C -5.695780 1.205081 0.000000 C -5.695780 -1.205081 0.000000 C 6.391533 0.000000 0.000000 C -6.391533 0.000000 0.000000 H 0.000000 0.000000 2.471513 H 0.000000 0.000000 -2.471513 H 0.000000 -2.140393 1.235756 H 0.000000 -2.140393 -1.235756 H 0.000000 2.140393 -1.235756 H 0.000000 2.140393 1.235756 H 2.528513 0.000000 0.000000 H -2.528513 0.000000 0.000000 H 3.764270 -2.140393 0.000000 H 3.764270 2.140393 0.000000 H -3.764270 2.140393 0.000000 H -3.764270 -2.140393 0.000000 H 6.235782 -2.140393 0.000000 H 6.235782 2.140393 0.000000 H -6.235782 2.140393 0.000000 H -6.235782 -2.140393 0.000000 H 7.471539 0.000000 0.000000 H -7.471539 0.000000 0.000000 MP2/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -230.72639830 !MP2 ENERGY -231.516608304077 ------ Table S4. Cartesian coordinates and total energies of the PD trimer C 3.400018 0.000000 0.858171 C -3.400018 0.000000 0.858171 C 3.400018 -1.205081 0.162418 C 3.400018 1.205081 0.162418 C -3.400018 -1.205081 0.162418 C -3.400018 1.205081 0.162418 C 3.400018 -1.205081 -1.229090 C 3.400018 1.205081 -1.229090 C -3.400018 -1.205081 -1.229090 C -3.400018 1.205081 -1.229090 C 3.400018 0.000000 -1.924843 C -3.400018 0.000000 -1.924843 C 0.000000 0.000000 -0.324835 C 0.000000 1.205081 0.370919 C 0.000000 -1.205081 0.370919 C 0.000000 1.205081 1.762426 C 0.000000 -1.205081 1.762426 C 0.000000 0.000000 2.458179 H 3.400018 0.000000 1.938177 H -3.400018 0.000000 1.938177 H 3.400018 -2.140393 0.702420 H 3.400018 2.140393 0.702420 H -3.400018 -2.140393 0.702420 H -3.400018 2.140393 0.702420 H 3.400018 -2.140393 -1.769093 H 3.400018 2.140393 -1.769093 H -3.400018 -2.140393 -1.769093 H -3.400018 2.140393 -1.769093 H 3.400018 0.000000 -3.004849 H -3.400018 0.000000 -3.004849 H 0.000000 0.000000 -1.404841 H 0.000000 2.140393 -0.169084 H 0.000000 -2.140393 -0.169084 H 0.000000 2.140393 2.302429 H 0.000000 -2.140393 2.302429 H 0.000000 0.000000 3.538185 CCSD(T)/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.16225929 MP2 total energy: -694.55677473 !CCSD(T) ENERGY -694.775390093188 ------ Table S5. Cartesian coordinates and total energies of the C trimer C 2.072533 0.400337 0.000000 C 2.351068 -0.237230 -1.205081 C 2.351068 -0.237230 1.205081 C 2.908137 -1.512363 -1.205081 C 2.908137 -1.512363 1.205081 C 3.186672 -2.149930 0.000000 C -1.382969 1.594698 0.000000 C -0.970087 2.154700 -1.205081 C -0.970087 2.154700 1.205081 C -0.144324 3.274703 -1.205081 C -0.144324 3.274703 1.205081 C 0.268558 3.834704 0.000000 C -0.689564 -1.995035 0.000000 C -1.380981 -1.917470 -1.205081 C -1.380981 -1.917470 1.205081 C -2.763814 -1.762339 -1.205081 C -2.763814 -1.762339 1.205081 C -3.455230 -1.684774 0.000000 H 1.640169 1.390021 0.000000 H 2.134886 0.257612 -2.140393 H 2.134886 0.257612 2.140393 H 3.124320 -2.007205 -2.140393 H 3.124320 -2.007205 2.140393 H 3.619036 -3.139614 0.000000 H -2.023878 0.725418 0.000000 H -1.290542 1.720059 -2.140393 H -1.290542 1.720059 2.140393 H 0.176131 3.709343 -2.140393 H 0.176131 3.709343 2.140393 H 0.909467 4.703984 0.000000 H 0.383709 -2.115439 0.000000 H -0.844344 -1.977672 -2.140393 H -0.844344 -1.977672 2.140393 H -3.300450 -1.702138 -2.140393 H -3.300450 -1.702138 2.140393 H -4.528503 -1.564371 0.000000 MP2/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.17237150 !MP2 ENERGY -694.559914277415 ------ Table S6. Cartesian coordinates and total energies of the S-PD trimer C -3.343091 1.733432 0.000000 C -3.514171 1.059040 -1.205081 C -3.514171 1.059040 1.205081 C -3.856332 -0.289744 -1.205081 C -3.856332 -0.289744 1.205081 C -4.027412 -0.964136 0.000000 C 0.340258 0.799037 0.000000 C 0.169177 0.124645 1.205081 C 0.169177 0.124645 -1.205081 C -0.172983 -1.224139 1.205081 C -0.172983 -1.224139 -1.205081 C -0.344063 -1.898531 0.000000 C 3.344994 -1.183685 0.000000 C 3.516074 -0.509293 1.205081 C 3.516074 -0.509293 -1.205081 C 3.858234 0.839491 1.205081 C 3.858234 0.839491 -1.205081 C 4.029315 1.513883 0.000000 H -3.077526 2.780278 0.000000 H -3.381389 1.582463 -2.140393 H -3.381389 1.582463 2.140393 H -3.989114 -0.813168 -2.140393 H -3.989114 -0.813168 2.140393 H -4.292977 -2.010983 0.000000 H 0.605823 1.845884 0.000000 H 0.301960 0.648068 2.140393 H 0.301960 0.648068 -2.140393 H -0.305765 -1.747562 2.140393 H -0.305765 -1.747562 -2.140393 H -0.609628 -2.945378 0.000000 H 3.079429 -2.230531 0.000000 H 3.383292 -1.032716 2.140393 H 3.383292 -1.032716 -2.140393 H 3.991017 1.362915 2.140393 H 3.991017 1.362915 -2.140393 H 4.294880 2.560730 0.000000 MP2/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.16305636 !MP2 ENERGY -694.553415791829 ------ Table S7. Cartesian coordinates and total energies of the S-T trimer C 1.391507 0.000000 4.200022 C -1.391507 0.000000 4.200022 C 0.695754 -1.205081 4.200022 C -0.695754 -1.205081 4.200022 C -0.695754 1.205081 4.200022 C 0.695754 1.205081 4.200022 C 1.391507 0.000000 0.400002 C -1.391507 0.000000 0.400002 C 0.695754 1.205081 0.400002 C -0.695754 1.205081 0.400002 C -0.695754 -1.205081 0.400002 C 0.695754 -1.205081 0.400002 C 0.000000 0.000000 -3.208517 C 0.000000 -1.205081 -3.904270 C 0.000000 1.205081 -3.904270 C 0.000000 -1.205081 -5.295778 C 0.000000 1.205081 -5.295778 C 0.000000 0.000000 -5.991531 H 2.471513 0.000000 4.200022 H -2.471513 0.000000 4.200022 H 1.235756 -2.140393 4.200022 H -1.235756 -2.140393 4.200022 H -1.235756 2.140393 4.200022 H 1.235756 2.140393 4.200022 H 2.471513 0.000000 0.400002 H -2.471513 0.000000 0.400002 H 1.235756 2.140393 0.400002 H -1.235756 2.140393 0.400002 H -1.235756 -2.140393 0.400002 H 1.235756 -2.140393 0.400002 H 0.000000 0.000000 -2.128511 H 0.000000 -2.140393 -3.364267 H 0.000000 2.140393 -3.364267 H 0.000000 -2.140393 -5.835780 H 0.000000 2.140393 -5.835780 H 0.000000 0.000000 -7.071537 MP2/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.16969885 !MP2 ENERGY -694.551041553090 ------ Table S8. Cartesian coordinates and total energies of the PD-T trimer C -3.808720 0.000000 1.034622 C -3.935229 -1.205081 0.350467 C -3.935229 1.205081 0.350467 C -4.188247 -1.205081 -1.017844 C -4.188247 1.205081 -1.017844 C -4.314756 0.000000 -1.701999 C -0.680487 0.000000 -0.746889 C -0.553978 1.205081 -0.062733 C -0.553978 -1.205081 -0.062733 C -0.300960 1.205081 1.305577 C -0.300960 -1.205081 1.305577 C -0.174451 0.000000 1.989733 C 3.120896 0.000000 -0.034716 C 3.805051 1.205081 -0.161225 C 3.805051 -1.205081 -0.161225 C 5.173362 1.205081 -0.414243 C 5.173362 -1.205081 -0.414243 C 5.857517 0.000000 -0.540752 H -3.612342 0.000000 2.096624 H -3.837040 -2.140393 0.881468 H -3.837040 2.140393 0.881468 H -4.286436 -2.140393 -1.548845 H -4.286436 2.140393 -1.548845 H -4.511133 0.000000 -2.764001 H -0.876864 0.000000 -1.808891 H -0.652167 2.140393 -0.593734 H -0.652167 -2.140393 -0.593734 H -0.202771 2.140393 1.836578 H -0.202771 -2.140393 1.836578 H 0.021927 0.000000 3.051735 H 2.058894 0.000000 0.161662 H 3.274050 2.140393 -0.063036 H 3.274050 -2.140393 -0.063036 H 5.704363 2.140393 -0.512432 H 5.704363 -2.140393 -0.512432 H 6.919519 0.000000 -0.737129 MP2/cc-pVDZ+ energies: !RHF STATE 1.1 ENERGY -692.16878445 !MP2 ENERGY -694.553964269193 ------ Table S9. Cartesian coordinates and total energies of the S tetramer C 1.391507 0.000000 -5.700030 C -1.391507 0.000000 -5.700030 C 0.695754 1.205081 -5.700030 C -0.695754 1.205081 -5.700030 C -0.695754 -1.205081 -5.700030 C 0.695754 -1.205081 -5.700030 C 1.391507 0.000000 -1.900010 C -1.391507 0.000000 -1.900010 C 0.695754 -1.205081 -1.900010 C -0.695754 -1.205081 -1.900010 C -0.695754 1.205081 -1.900010 C 0.695754 1.205081 -1.900010 C 1.391507 0.000000 1.900010 C -1.391507 0.000000 1.900010 C 0.695754 -1.205081 1.900010 C -0.695754 -1.205081 1.900010 C -0.695754 1.205081 1.900010 C 0.695754 1.205081 1.900010 C 1.391507 0.000000 5.700030 C -1.391507 0.000000 5.700030 C 0.695754 -1.205081 5.700030 C -0.695754 -1.205081 5.700030 C -0.695754 1.205081 5.700030 C 0.695754 1.205081 5.700030 H 2.471513 0.000000 -5.700030 H -2.471513 0.000000 -5.700030 H 1.235756 2.140393 -5.700030 H -1.235756 2.140393 -5.700030 H -1.235756 -2.140393 -5.700030 H 1.235756 -2.140393 -5.700030 H 2.471513 0.000000 -1.900010 H -2.471513 0.000000 -1.900010 H 1.235756 -2.140393 -1.900010 H -1.235756 -2.140393 -1.900010 H -1.235756 2.140393 -1.900010 H 1.235756 2.140393 -1.900010 H 2.471513 0.000000 1.900010 H -2.471513 0.000000 1.900010 H 1.235756 -2.140393 1.900010 H -1.235756 -2.140393 1.900010 H -1.235756 2.140393 1.900010 H 1.235756 2.140393 1.900010 H 2.471513 0.000000 5.700030 H -2.471513 0.000000 5.700030 H 1.235756 -2.140393 5.700030 H -1.235756 -2.140393 5.700030 H -1.235756 2.140393 5.700030 H 1.235756 2.140393 5.700030 MP2/cc-pVDZ+ energies: (gdirect,thrmax_dscf=1.0E-10,dmp2=0) !RHF STATE 1.1 ENERGY -922.88245031 !MP2 ENERGY -926.069106216865 ------ Table S10. Cartesian coordinates and total energies of the T tetramer C 1.391507 0.000000 7.500039 C -1.391507 0.000000 7.500039 C 0.695754 -1.205081 7.500039 C -0.695754 -1.205081 7.500039 C -0.695754 1.205081 7.500039 C 0.695754 1.205081 7.500039 C 0.000000 0.000000 3.891520 C 0.000000 -1.205081 3.195767 C 0.000000 1.205081 3.195767 C 0.000000 -1.205081 1.804259 C 0.000000 1.205081 1.804259 C 0.000000 0.000000 1.108506 C 1.391507 0.000000 -2.500013 C -1.391507 0.000000 -2.500013 C 0.695754 1.205081 -2.500013 C -0.695754 1.205081 -2.500013 C -0.695754 -1.205081 -2.500013 C 0.695754 -1.205081 -2.500013 C 0.000000 0.000000 -6.108532 C 0.000000 -1.205081 -6.804285 C 0.000000 1.205081 -6.804285 C 0.000000 -1.205081 -8.195793 C 0.000000 1.205081 -8.195793 C 0.000000 0.000000 -8.891546 H 2.471513 0.000000 7.500039 H -2.471513 0.000000 7.500039 H 1.235756 -2.140393 7.500039 H -1.235756 -2.140393 7.500039 H -1.235756 2.140393 7.500039 H 1.235756 2.140393 7.500039 H 0.000000 0.000000 4.971526 H 0.000000 -2.140393 3.735769 H 0.000000 2.140393 3.735769 H 0.000000 -2.140393 1.264257 H 0.000000 2.140393 1.264257 H 0.000000 0.000000 0.028500 H 2.471513 0.000000 -2.500013 H -2.471513 0.000000 -2.500013 H 1.235756 2.140393 -2.500013 H -1.235756 2.140393 -2.500013 H -1.235756 -2.140393 -2.500013 H 1.235756 -2.140393 -2.500013 H 0.000000 0.000000 -5.028526 H 0.000000 -2.140393 -6.264283 H 0.000000 2.140393 -6.264283 H 0.000000 -2.140393 -8.735795 H 0.000000 2.140393 -8.735795 H 0.000000 0.000000 -9.971552 MP2/cc-pVDZ+ energies: (gdirect,thrmax_dscf=1.0E-10,dmp2=0) !RHF STATE 1.1 ENERGY -922.89912399 !MP2 ENERGY -926.070845777728 ------ Table S11. Cartesian coordinates and total energies of the PD tetramer C -5.009212 1.126028 0.000000 C 5.009212 -1.126028 0.000000 C -5.082583 0.434154 -1.205081 C -5.082583 0.434154 1.205081 C 5.082583 -0.434154 1.205081 C 5.082583 -0.434154 -1.205081 C -5.229324 -0.949594 -1.205081 C -5.229324 -0.949594 1.205081 C 5.229324 0.949594 1.205081 C 5.229324 0.949594 -1.205081 C -5.302695 -1.641468 0.000000 C 5.302695 1.641468 0.000000 C -1.752907 -0.408930 0.000000 C 1.752907 0.408930 0.000000 C -1.679536 0.282944 1.205081 C -1.679536 0.282944 -1.205081 C 1.679536 -0.282944 -1.205081 C 1.679536 -0.282944 1.205081 C -1.532795 1.666692 1.205081 C -1.532795 1.666692 -1.205081 C 1.532795 -1.666692 -1.205081 C 1.532795 -1.666692 1.205081 C -1.459424 2.358566 0.000000 C 1.459424 -2.358566 0.000000 H -4.895320 2.200012 0.000000 H 4.895320 -2.200012 0.000000 H -5.025637 0.971146 -2.140393 H -5.025637 0.971146 2.140393 H 5.025637 -0.971146 2.140393 H 5.025637 -0.971146 -2.140393 H -5.286270 -1.486586 -2.140393 H -5.286270 -1.486586 2.140393 H 5.286270 1.486586 2.140393 H 5.286270 1.486586 -2.140393 H -5.416587 -2.715452 0.000000 H 5.416587 2.715452 0.000000 H -1.866799 -1.482914 0.000000 H 1.866799 1.482914 0.000000 H -1.736482 -0.254048 2.140393 H -1.736482 -0.254048 -2.140393 H 1.736482 0.254048 -2.140393 H 1.736482 0.254048 2.140393 H -1.475849 2.203684 2.140393 H -1.475849 2.203684 -2.140393 H 1.475849 -2.203684 -2.140393 H 1.475849 -2.203684 2.140393 H -1.345532 3.432550 0.000000 H 1.345532 -3.432550 0.000000 MP2/cc-pVDZ+ energies: (gdirect,thrmax_dscf=1.0E-10,dmp2=0) !RHF STATE 1.1 ENERGY -922.88042032 !MP2 ENERGY -926.079453506593 ------