Dear Molcas users,
a long time ago (in Molcas version 6.4), during a routine change of the ANO-RCC basis set there was a human mistake resulting the basis set for C atom being wrong.
The error was recently discovered (thanks to Patrick Zobel !), and now we have constructed the corrected basis set.
Small test calculations (e.g. BSSE, geometry) have shown that there are significant errors to be found at least up till QZ, and only for very large contractions one can expect the errors to become small, if at all. These small test calculations are in no way representative for the many systems and properties people are studying. Therefore, the only correct way to assess the impact of the erroneous basis set for you personally is to compare the results for your particular system(s) and property with the correct basis set.
We prepared some comparison, including three variants: You can also download the complete and corrected ANO-RCC file


On the behalf of the Molcas team,
Per-Olof Widmark, Roland Lindh, Per-Åke Malmqvist, Steven Vancoillie, Victor Vysotskiy, Valera Veryazov.

Table 1
Contraction errors for the ANO-RCC primitives 14s9p4d3f2g for C atom. 

States are: C^+ 2P(s2p), C 3P(s2p2) and C^- 4S(s2p3)
Total energies
---------------------------------------------------------------------------------------------
Basis            2P(scf)      2P(sdci)      3P(scf)      3P(sdci)      4S(scf)      4S(sdci)
-----------   ------------ ------------  ------------ ------------  ------------ ------------

Before:
3s2p1d        -37.30668462 -37.37918902  -37.70282066 -37.78483975  -37.69945519 -37.79185910
4s3p2d1f      -37.30689419 -37.38710385  -37.70335850 -37.79669353  -37.71181984 -37.82222318
5s4p3d2f1g    -37.30718379 -37.38917604  -37.70345706 -37.79940790  -37.71873710 -37.83409015
6s5p4d3f2g    -37.30727003 -37.38961611  -37.70351374 -37.79992469  -37.72099344 -37.83743655
14s9p4d3f2g   -37.30728148 -37.38972496  -37.70352240 -37.80004059  -37.72362520 -37.84128804

After:
3s2p1d        -37.28276900 -37.35578398  -37.68026212 -37.76189764  -37.68799171 -37.78060488
4s3p2d1f      -37.28741867 -37.36711700  -37.68471891 -37.77770894  -37.69995131 -37.81103048
5s4p3d2f1g    -37.29260204 -37.37450341  -37.68959647 -37.78542442  -37.70685568 -37.82235705
6s5p4d3f2g    -37.30078991 -37.38308752  -37.69704176 -37.79341467  -37.71581111 -37.83254051
14s9p4d3f2g   -37.30728148 -37.38972496  -37.70352240 -37.80004059  -37.72362520 -37.84128804

Fixed:
3s2p1d        -37.30694503 -37.38012883  -37.70311914 -37.78535091  -37.70272840 -37.79481771
4s3p2d1f      -37.30705094 -37.38719388  -37.70341882 -37.79676493  -37.71252977 -37.82307672
5s4p3d2f1g    -37.30723473 -37.38924769  -37.70346569 -37.79944554  -37.71858039 -37.83386776
6s5p4d3f2g    -37.30727722 -37.38963360  -37.70351709 -37.79994101  -37.72075656 -37.83712874
14s9p4d3f2g   -37.30728148 -37.38972496  -37.70352240 -37.80004059  -37.72362520 -37.84128804
Table 2
Convergence of RASSCF energy for C atom CAS(2s,2p) 3P state with basis set size 
          Before        After         Fixed                     
2s1p     -37.71403268  -37.69596741  -37.71557040 
3s2p1d   -37.72037182  -37.69773387  -37.72062950 
4s3p2d1f -37.72072957  -37.70207070  -37.72078355 
5s4p3d2f -37.72081304  -37.70693083  -37.72081932 
8s7p4d3f -37.72086831  -37.72028072  -37.72086825
Table 3
C BSSE in CO at R_(C-O) = 1.2Å 

                  E_SCF_UHF(C)   E_SCF_UHF(CO)  BSSE          E_MP2(C)       E_MP2(CO)      BSSE
                  (hartree)      (hartree)      (kcal/mol)    (hartree)      (hartree)      (kcal/mol)
Before
VDZP(3s2p1d)      -37.7078768277 -37.7079684649  0.06         -37.8116415124 -37.8149961416  2.11
VTZP(4s3p2d1f)    -37.7084105092 -37.7084567655  0.03         -37.8496594152 -37.8517055818  1.28
VQZP(5s4p3d2f1g)  -37.7085182733 -37.7085746308  0.04         -37.8628450963 -37.8640305596  0.74
 
After
VDZP(3s2p1d)      -37.6851800447 -37.6854232152  0.15         -37.7871781736 -37.7903104481  1.97
VTZP(4s3p2d1f)    -37.6898381102 -37.6959717048  3.85         -37.8302015482 -37.8383151704  5.09
VQZP(5s4p3d2f1g)  -37.6946811422 -37.7031014017  5.28         -37.8487205378 -37.8582374785  5.97
 
Fixed
VDZP(3s2p1d)      -37.7079796742 -37.7081528682  0.11         -37.8129042215 -37.8160191749  1.95
VTZP(4s3p2d1f)    -37.7084816440 -37.7085109773  0.02         -37.8496315042 -37.8516480489  1.27
VQZP(5s4p3d2f1g)  -37.7085477079 -37.7085847165  0.02         -37.8628195585 -37.8639909204  0.74


CAS(3,4) with 2s,2p active
                   E_RASSCF(C)    E_RASSCF(CO)   BSSE          E_CASPT2(C)    E_CASPT2(CO)   BSSE
                   (hartree)      (hartree)      (kcal/mol)    (hartree)      (hartree)      (kcal/mol)

Before
VDZP(3s2p1d)      -37.72146104   -37.72170627    0.15         -37.77148857   -37.77319583    1.07
VTZP(4s3p2d1f)    -37.72267284   -37.72271895    0.03         -37.78516792   -37.78628467    0.70
VQZP(5s4p3d2f1g)  -37.72281994   -37.72284621    0.02         -37.78927831   -37.79002963    0.47
 
After
VDZP(3s2p1d)      -37.69909282   -37.69942244    0.21         -37.74897396   -37.75064222    1.05
VTZP(4s3p2d1f)    -37.70393532   -37.71014058    3.89         -37.76611731   -37.77337026    4.55
VQZP(5s4p3d2f1g)  -37.70890648   -37.71735037    5.30         -37.77526721   -37.78447753    5.78
 
Fixed                                       
VDZP(3s2p1d)      -37.72174061   -37.72201903    0.17         -37.77222509   -37.77386566    1.03
VTZP(4s3p2d1f)    -37.72273500   -37.72276271    0.02         -37.78520392   -37.78630270    0.69
VQZP(5s4p3d2f1g)  -37.72282900   -37.72284775    0.01         -37.78930060   -37.78972280    0.26
Table 4
Carbon dimer at r(CC)=1.25 (Angstrom)
Total energies shifted by 70 a.u. 
 CASSCF 8/8, 4 roots average optimization

                  Ground state; 1^1\Delta (2 roots); 2^1A^{+}

Before
3s2p1d.          -5.65188932 -5.56349472 -5.56349472 -5.55887774
4s3p2d1f.        -5.65623015 -5.56763908 -5.56763908 -5.56341566
5s4p3d2f1g.      -5.65705010 -5.56841914 -5.56841914 -5.56420988
6s5p4d3f2g.      -5.65715650 -5.56855030 -5.56855030 -5.56433581
8s7p4d3f2g.      -5.65719634 -5.56860779 -5.56860779 -5.56439174

After
3s2p1d.          -5.60973910 -5.52016462 -5.52016462 -5.51574449
4s3p2d1f.        -5.63339027 -5.54474769 -5.54474769 -5.54054283
5s4p3d2f1g.      -5.64836253 -5.55956786 -5.55956786 -5.55536280
6s5p4d3f2g.      -5.65205524 -5.56340785 -5.56340785 -5.55919363
8s7p4d3f2g.      -5.65605501 -5.56745887 -5.56745887 -5.56324407

Fixed
3s2p1d.          -5.65210630 -5.56301913 -5.56301913 -5.55846413
4s3p2d1f.        -5.65583992 -5.56727145 -5.56727145 -5.56304318
5s4p3d2f1g.      -5.65694348 -5.56830429 -5.56830429 -5.56409214
6s5p4d3f2g.      -5.65713320 -5.56852606 -5.56852606 -5.56431235
8s7p4d3f2g.      -5.65719512 -5.56860603 -5.56860603 -5.56438993

 Standard CASPT2

                 Ground state; 1^1\Delta (2 roots); 2^1A^{+}

Before
3s2p1d.          -5.76577865 -5.68071797 -5.68071892 -5.67084910
4s3p2d1f.        -5.80644346 -5.72346646 -5.72351205 -5.71320164
5s4p3d2f1g.      -5.81847737 -5.73645942 -5.73635199 -5.72589321
6s5p4d3f2g.      -5.82032764 -5.73829990 -5.73826914 -5.72785802
8s7p4d3f2g.      -5.82056440 -5.73866858 -5.73867938 -5.72821006

After
3s2p1d.          -5.72237282 -5.63652049 -5.63648547 -5.62674413
4s3p2d1f.        -5.78251276 -5.69940194 -5.69941406 -5.68908712
5s4p3d2f1g.      -5.80949060 -5.72720191 -5.72720374 -5.71673663
6s5p4d3f2g.      -5.81522643 -5.73311546 -5.73308767 -5.72263978
8s7p4d3f2g.      -5.81942295 -5.73750965 -5.73751984 -5.72706423

Fixed
3s2p1d.          -5.76688386 -5.68123063 -5.68113153 -5.67137362
4s3p2d1f.        -5.80573313 -5.72281847 -5.72279272 -5.71245171
5s4p3d2f1g.      -5.81829209 -5.73610403 -5.73613775 -5.72566605
6s5p4d3f2g.      -5.82033482 -5.73830264 -5.73830801 -5.72786627
8s7p4d3f2g.      -5.82058655 -5.73866772 -5.73869656 -5.72820793
Table 5
Geometry optimization (MP2) for C-C distance
Ethane:

Contraction       r(C-C), A
C   H            After    Fixed
DZ DZ            1.524    1.528
TZ DZ            1.505    1.524
QZ DZ            1.483    1.522


Ethene:

Contraction       r(C-C), A
C  H             After    Fixed
DZ DZ            1.339    1.339
TZ DZ            1.316    1.332
QZ DZ            1.319    1.332
Table 6
MS-CASPT2(4,4) (2pi+2pi*) vertical excitation energies (eV) 
E-butadiene:

          1 ^1B_1u  2 ^1A_1g  1 ^3B_1u 1 ^3A_1g 
VDZP
Before     6.694     6.802     3.389    5.273
After      6.659     6.709     3.353    5.203
Fixed      6.655     6.782     3.379    5.255
          
VTZP      
Before     6.350     6.639     3.353    5.177
After      6.298     6.608     3.344    5.161
Fixed      6.346     6.636     3.351    5.175
          
          
Nornbornadiene:
          
         1 ^1A_2  1 ^1B_2  2 ^1B_2  2 ^1A_2  1 ^3A_2  1 ^3B_2
VDZP       
Before     5.446    7.088    8.246    7.678    3.794    4.267
After      5.345    6.437    7.999    7.553    3.743    4.219
Fixed      5.427    6.897    8.201    7.653    3.782    4.256
                    
VTZP
Before     5.958    7.058    7.412    7.827    3.726    4.207
After      5.911    7.062    7.407    7.827    3.710    4.195
Fixed      5.985    7.057    7.410    7.836    3.723    4.205